Editorial: use VoidFunction instead of Function in queueMicrotask()

queueMicrotask() doesn't pass any arguments or return any values, so
VoidFunction is a better fit than Function. This does not change the
processing model, but is easier for implementers and code generators.

source

@@ -2951,6 +2951,7 @@ a.setAttribute('href', 'https://example.com/'); // change the content attribute
      <li><dfn data-x="idl-unrestricted-double" data-x-href="https://heycam.github.io/webidl/#idl-unrestricted-double"><code>unrestricted double</code></dfn></li>
      <li><dfn data-x="idl-unsigned-long" data-x-href="https://heycam.github.io/webidl/#idl-unsigned-long"><code>unsigned long</code></dfn></li>
      <li><dfn data-x="idl-USVString" data-x-href="https://heycam.github.io/webidl/#idl-USVString"><code>USVString</code></dfn></li>
+     <li><dfn data-x="idl-VoidFunction" data-x-href="https://heycam.github.io/webidl/#VoidFunction"><code>VoidFunction</code></dfn></li>
     </ul>
 
     <p>The term <dfn data-x-href="https://heycam.github.io/webidl/#dfn-throw">throw</dfn> in this
@@ -90673,7 +90674,7 @@ interface mixin <dfn>WindowOrWorkerGlobalScope</dfn> {
   void <span data-x="dom-clearInterval">clearInterval</span>(optional long handle = 0);
 
   // microtask queuing
-  void <span data-x="dom-queueMicrotask">queueMicrotask</span>(<span data-x="idl-Function">Function</span> <var>callback</var>);
+  void <span data-x="dom-queueMicrotask">queueMicrotask</span>(<span data-x="idl-VoidFunction">VoidFunction</span> <var>callback</var>);
 
   // ImageBitmap
   Promise&lt;<span>ImageBitmap</span>&gt; <span data-x="dom-createImageBitmap">createImageBitmap</span>(<span>ImageBitmapSource</span> image, optional <span>ImageBitmapOptions</span> options);