Allow <script> inside <hgroup>

This was introduced in c9a38bd and then removed in d2021df for unspecified reasons.

source

@@ -16012,7 +16012,9 @@ interface <dfn>HTMLHeadingElement</dfn> : <span>HTMLElement</span> {};</pre>
    <dt><span data-x="concept-element-contexts">Contexts in which this element can be used</span>:</dt>
    <dd>Where <span>flow content</span> is expected.</dd>
    <dt><span data-x="concept-element-content-model">Content model</span>:</dt>
-   <dd>One or more <code>h1</code>, <code>h2</code>, <code>h3</code>, <code>h4</code>, <code>h5</code>, <code>h6</code>, and <code>template</code> elements.</dd>
+   <dd>One or more <code>h1</code>, <code>h2</code>, <code>h3</code>, <code>h4</code>,
+   <code>h5</code>, <code>h6</code> elements, optionally intermixed with <span>script-supporting
+   elements</span>.</dd>
    <dt><span data-x="concept-element-attributes">Content attributes</span>:</dt>
    <dd><span>Global attributes</span></dd>
    <dt><span data-x="concept-element-dom">DOM interface</span>:</dt>
@@ -116210,7 +116212,13 @@ interface <dfn>External</dfn> {
          <span data-x="Heading content">heading</span>;
          <span data-x="Palpable content">palpable</span></td>
      <td><span data-x="Flow content">flow</span></td>
-     <td>One or more <code>h1</code>, <code>h2</code>, <code>h3</code>, <code>h4</code>, <code>h5</code>, <code>h6</code>, and <code>template</code></td>
+     <td><code>h1</code>;
+         <code>h2</code>;
+         <code>h3</code>;
+         <code>h4</code>;
+         <code>h5</code>;
+         <code>h6</code>;
+         <span>script-supporting elements</span></td>
      <td><span data-x="global attributes">globals</span></td>
      <td><code>HTMLElement</code></td>
     </tr>