Editorial: minor fixes to the parse error table (whatwg#2728)

Element names in the domTree should be lowercase. Also add comma
and space after "e.g.".

source

@@ -100430,12 +100430,12 @@ dictionary <dfn>StorageEventInit</dfn> : <span>EventInit</span> {
 
        <p>This will be parsed into:</p>
 
-       <ul class="domTree"><li class="t8"><code>#comment</code>: <span data-x="">?xml-stylesheet type="text/css" href="style.css"?</span></li><li class="t1"><code>HTML</code><ul><li class="t1"><code>HEAD</code></li><li class="t1"><code>BODY</code></li></ul></li></ul>
+       <ul class="domTree"><li class="t8"><code>#comment</code>: <span data-x="">?xml-stylesheet type="text/css" href="style.css"?</span></li><li class="t1"><code>html</code><ul><li class="t1"><code>head</code></li><li class="t1"><code>body</code></li></ul></li></ul>
       </div>
 
       <p class="note">The common reason for this error is an XML processing instruction (e.g., <code
       data-x="">&lt;?xml-stylesheet type="text/css" href="style.css"?></code>) or an XML declaration
-      (e.g.<code data-x="">&lt;?xml version="1.0" encoding="UTF-8" ?></code>) being used in
+      (e.g., <code data-x="">&lt;?xml version="1.0" encoding="UTF-8"?></code>) being used in
       HTML.</p>
 
     <tr>