Editorial: use Infra's remove operation for top layer

With whatwg/fullscreen#79, the top layer is just
an ordered set, and the remove operation does not need any indirection.

source

@@ -3155,9 +3155,10 @@ a.setAttribute('href', 'https://example.com/'); // change the content attribute
     define how the Fullscreen API interacts with HTML: <ref spec=FULLSCREEN></p>
 
     <ul class="brief">
-     <li><dfn data-x-href="https://fullscreen.spec.whatwg.org/#top-layer">top layer</dfn> and its
-         <dfn data-x="top-layer-add" data-x-href="https://fullscreen.spec.whatwg.org/#top-layer-add">add</dfn> and
-         <dfn data-x="top-layer-remove" data-x-href="https://fullscreen.spec.whatwg.org/#top-layer-remove">remove</dfn> algorithms</li>
+     <li><dfn data-x-href="https://fullscreen.spec.whatwg.org/#top-layer">top layer</dfn> (an
+         <span data-x="set">ordered set</span>) and its
+         <dfn data-x="top-layer-add" data-x-href="https://fullscreen.spec.whatwg.org/#top-layer-add">add</dfn>
+         operation</li>
      <li><dfn data-x-href="https://fullscreen.spec.whatwg.org/#dom-element-requestfullscreen"><code data-x="dom-element-requestFullscreen">requestFullscreen()</code></dfn></li>
     </ul>
 
@@ -57264,7 +57265,7 @@ interface <dfn>HTMLDialogElement</dfn> : <span>HTMLElement</span> {
 
   <p>When an element is added to the <span>pending dialog stack</span>, it must also be <span
   data-x="top-layer-add">added</span> to the <span>top layer</span>. When an element is removed from
-  the <span>pending dialog stack</span>, it must be <span data-x="top-layer-remove">removed</span>
+  the <span>pending dialog stack</span>, it must be <span data-x="list remove">removed</span>
   from the <span>top layer</span>. <ref spec=FULLSCREEN></p>
 
   <p>When the <dfn><code data-x="dom-dialog-showModal">showModal()</code></dfn> method is invoked,