Expunge “HTMLObjectElement: typeMustMatch”

This change deletes the Web/API/HTMLObjectElement/typeMustMatch
article, as well as expunging all references to it from other articles.
The change also drops all mentions of the corresponding “typemustmatch”
markup attribute for “object” elements.

The history of typeMustMatch/typemustmatch is that it was added to the
spec in 2011 in whatwg/html@4030e71 but never
got implemented across browsers and never got adopted by web developers.
So whatwg/html#4590 dropped it from the spec in
2019, and it's now just a footnote in the “Non-conforming features” section
at https://html.spec.whatwg.org/obsolete.html#attr-object-typemustmatch

So there's statistically near-zero content on the web that’s using
typeMustMatch/typemustmatch, and there’s no value to continue
documenting it in MDN.

files/en-us/_redirects.txt

@@ -1,3 +1,8 @@
+# DO NOT EDIT THIS FILE MANUALLY.
+# Use the CLI instead:
+#
+#    yarn content add-redirect <fromURL> <toURL>
+#
 # FROM-URL	TO-URL
 /en-US/docs/-moz-locale-dir(ltr)	/en-US/docs/Web/CSS/:-moz-locale-dir(ltr)
 /en-US/docs/-moz-locale-dir(rtl)	/en-US/docs/Web/CSS/:-moz-locale-dir(rtl)
@@ -7941,7 +7946,6 @@
 /en-US/docs/Web/API/HTMLLinkElement.relList	/en-US/docs/Web/API/HTMLLinkElement/relList
 /en-US/docs/Web/API/HTMLMediaElement/Web_audio:_ended_event	/en-US/docs/Web/API/AudioScheduledSourceNode/ended_event
 /en-US/docs/Web/API/HTMLMediaElement/mcs_ended_event	/en-US/docs/Web/API/MediaStreamTrack/ended_event
-/en-US/docs/Web/API/HTMLObjectElement.typeMustMatch	/en-US/docs/Web/API/HTMLObjectElement/typeMustMatch
 /en-US/docs/Web/API/HTMLObjectElement/tabIndex	/en-US/docs/Web/API/HTMLObjectElement/type
 /en-US/docs/Web/API/HTMLOptionElement.Option	/en-US/docs/Web/API/HTMLOptionElement/Option
 /en-US/docs/Web/API/HTMLOrSVGElement	/en-US/docs/Web/API/HTMLOrForeignElement

files/en-us/_wikihistory.json

@@ -57188,17 +57188,6 @@
       "jpmedley"
     ]
   },
-  "Web/API/HTMLObjectElement/typeMustMatch": {
-    "modified": "2020-10-15T21:29:52.384Z",
-    "contributors": [
-      "sideshowbarker",
-      "jpmedley",
-      "mfluehr",
-      "connorshea",
-      "fscholz",
-      "teoli"
-    ]
-  },
   "Web/API/HTMLObjectElement/useMap": {
     "modified": "2020-10-15T22:17:32.888Z",
     "contributors": [

files/en-us/learn/html/multimedia_and_embedding/other_embedding_technologies/index.html

@@ -330,10 +330,6 @@ <h2 id="The_&lt;embed&gt;_and_&lt;object&gt;_elements">The &lt;embed&gt; and &lt
  </tbody>
 </table>
 
-<div class="note">
-<p><strong>Note</strong>: <code>&lt;object&gt;</code> requires a <code>data</code> attribute, a <code>type</code> attribute, or both. If you use both, you may also use the {{htmlattrxref('typemustmatch','object')}} attribute (only implemented in Firefox and Chrome, as of this writing). <code>typemustmatch</code> keeps the embedded file from running unless the <code>type</code> attribute provides the correct media type. <code>typemustmatch</code> can therefore confer significant security benefits when you're embedding content from a different {{glossary("origin")}} (it can keep attackers from running arbitrary scripts through the plugin).</p>
-</div>
-
 <p>Here's an example that uses the {{htmlelement("embed")}} element to embed a Flash movie (see this <a href="https://mdn.github.io/learning-area/html/multimedia-and-embedding/other-embedding-technologies/embed-flash.html">live on GitHub</a>, and <a href="https://github.com/mdn/learning-area/blob/gh-pages/html/multimedia-and-embedding/other-embedding-technologies/embed-flash.html">check the source code</a> too):</p>
 
 <pre class="brush: html">&lt;embed src="whoosh.swf" quality="medium"
@@ -347,7 +343,7 @@ <h2 id="The_&lt;embed&gt;_and_&lt;object&gt;_elements">The &lt;embed&gt; and &lt
 <p>Now let's look at an <code>&lt;object&gt;</code> example that embeds a PDF into a page (see the <a href="https://mdn.github.io/learning-area/html/multimedia-and-embedding/other-embedding-technologies/object-pdf.html">live example</a> and the <a href="https://github.com/mdn/learning-area/blob/gh-pages/html/multimedia-and-embedding/other-embedding-technologies/object-pdf.html">source code</a>):</p>
 
 <pre class="brush: html">&lt;object data="mypdf.pdf" type="application/pdf"
-        width="800" height="1200" typemustmatch&gt;
+        width="800" height="1200"&gt;
   &lt;p&gt;You don't have a PDF plugin, but you can
     &lt;a href="mypdf.pdf"&gt;download the PDF file.
     &lt;/a&gt;

files/en-us/web/api/htmlobjectelement/index.html

@@ -54,8 +54,6 @@ <h2 id="Properties">Properties</h2>
  <dd>Is a <code>long</code> representing the position of the element in the tabbing navigation order for the current document.</dd>
  <dt>{{domxref("HTMLObjectElement.type")}}</dt>
  <dd>Is a {{domxref("DOMString")}} that reflects the {{htmlattrxref("type", "object")}} HTML attribute, specifying the MIME type of the resource.</dd>
- <dt>{{domxref("HTMLObjectElement.typeMustMatch")}}</dt>
- <dd>Is a {{jsxref("Boolean")}} that reflects the {{htmlattrxref("typeMustMatch", "object")}} HTML attribute, indicating if the resource specified by {{htmlattrxref("data", "object")}} must only be played if it matches the {{htmlattrxref("type", "object")}} attribute.</dd>
  <dt>{{domxref("HTMLObjectElement.useMap")}}</dt>
  <dd>Is a {{domxref("DOMString")}} that reflects the {{htmlattrxref("usemap", "object")}} HTML attribute, specifying a {{HTMLElement("map")}} element to use.</dd>
  <dt>{{domxref("HTMLObjectElement.validationMessage")}} {{readonlyInline}}</dt>
@@ -95,15 +93,6 @@ <h2 id="Specifications">Specifications</h2>
    <td>{{Spec2('HTML WHATWG')}}</td>
    <td></td>
   </tr>
-  <tr>
-   <td>{{SpecName('HTML5 W3C', "embedded-content-0.html#the-object-element", "HTMLObjectElement")}}</td>
-   <td>{{Spec2('HTML5 W3C')}}</td>
-   <td>The W3C specification is a latest of a previous version of {{SpecName("HTML WHATWG")}}<br>
-    Technically, the property <code>tabindex</code> is now defined on {{domxref("HTMLElement")}}.<br>
-    The following properties are now obsolete: <code>align</code>, <code>archive</code>, <code>border</code>, <code>code</code>, <code>codeBase</code>, <code>codeType</code>, <code>declare</code>, <code>hspace</code>, <code>standby</code>, and <code>vspace</code>.<br>
-    The following properties have been added: <code>typeMustMatch</code>, <code>contentWindow</code>, <code>willValidate</code>, <code>validity</code>, and <code>validationMessage</code>.<br>
-    The following methods have been added: <code>checkValidity()</code> and <code>setCustomValidity()</code>.</td>
-  </tr>
   <tr>
    <td>{{SpecName('DOM2 HTML', 'html.html#ID-9893177', 'HTMLObjectElement')}}</td>
    <td>{{Spec2('DOM2 HTML')}}</td>

files/en-us/web/html/element/object/index.html

@@ -80,8 +80,6 @@ <h2 id="Attributes">Attributes</h2>
  <dd>The position of the element in the tabbing navigation order for the current document.</dd>
  <dt>{{HTMLAttrDef("type")}}</dt>
  <dd>The <a href="/en-US/docs/Glossary/MIME_type">content type</a> of the resource specified by <strong>data</strong>. At least one of <strong>data</strong> and <strong>type</strong> must be defined.</dd>
- <dt>{{HTMLAttrDef("typemustmatch")}}</dt>
- <dd>This Boolean attribute indicates if the <strong>type</strong> attribute and the actual <a href="/en-US/docs/Glossary/MIME_type">content type</a> of the resource must match to be used.</dd>
  <dt>{{HTMLAttrDef("usemap")}}</dt>
  <dd>A hash-name reference to a {{HTMLElement("map")}} element; that is a '#' followed by the value of a {{htmlattrxref("name", "map")}} of a map element.</dd>
  <dt>{{HTMLAttrDef("width")}}</dt>