Remove UA styles for h1 in article, aside, nav, section

Fixes #7867.

Author: zcorpan

source

@@ -137396,19 +137396,6 @@ h4 { margin-block: 1.33em; font-size: 1.00em; font-weight: bold; }
 h5 { margin-block: 1.67em; font-size: 0.83em; font-weight: bold; }
 h6 { margin-block: 2.33em; font-size: 0.67em; font-weight: bold; }</code></pre>
 
-  <p>In the following CSS block, <var>x</var> is shorthand for the following selector:
-  <code data-x="">:is(article, aside, nav, section)</code></p>
-
-  <pre><code class="css">@namespace "http://www.w3.org/1999/xhtml";
-
-<var>x</var> h1 { margin-block: 0.83em; font-size: 1.50em; }
-<var>x</var> <var>x</var> h1 { margin-block: 1.00em; font-size: 1.17em; }
-<var>x</var> <var>x</var> <var>x</var> h1 { margin-block: 1.33em; font-size: 1.00em; }
-<var>x</var> <var>x</var> <var>x</var> <var>x</var> h1 { margin-block: 1.67em; font-size: 0.83em; }
-<var>x</var> <var>x</var> <var>x</var> <var>x</var> <var>x</var> h1 { margin-block: 2.33em; font-size: 0.67em; }</code></pre>
-
-  <p class="note">The shorthand is used to keep this block at least mildly readable.</p>
-
 
 
   <h4>Lists</h4>