[css-pseudo-4] Fix markup

Author: fantasai

css-pseudo-4/Overview.bs

@@ -561,13 +561,13 @@ Styling Highlights</h3>
 Default UA Styles</h3>
 
   The following additions are recommended for the default UA stylesheet:
-  <pre><code class="lang-css">
+  <pre class="lang-css">
     /* Represent default spelling/grammar error styling in an adjustable way */
     :root::spelling-error { text-decoration-line: spelling-error; }
     :root::grammar-error  { text-decoration-line: grammar-error; }
     /* Highlight targetted text */
     :root::target-text    { color: MarkText; background: Mark; }
-  </code></pre>
+  </pre>
 
   UAs may apply additional effects to enhance the presentation
   of highlighted content,