Add <param> to the "serializes as void" list

This regressed in 04a11f2, which removed <param> from the list of "void elements" (since it is no longer a conforming element), without adding it to the parser-algorithm-focused "serializes as void" list.

Closes #9249.

source

@@ -122611,7 +122611,7 @@ document.body.appendChild(text);
 
   <p>For the purposes of the following algorithm, an element <dfn>serializes as void</dfn> if its
   element type is one of the <span>void elements</span>, or is <code>basefont</code>,
-  <code>bgsound</code>, <code>frame</code>, or <code>keygen</code>.</p>
+  <code>bgsound</code>, <code>frame</code>, <code>keygen</code>, or <code>param</code>.</p>
 
   <p>The following steps form the <!--en-GB--><dfn id="html-fragment-serialisation-algorithm"
   export>HTML fragment serialization algorithm</dfn>. The algorithm takes as input a DOM