[css-pseudo-4] Fix broken example. :(

Author: fantasai

css-pseudo-4/Overview.bs

@@ -592,21 +592,22 @@ Cascading and Per-Element Highlight Styles</h3>
   <div class="example">
     For example, if an author specified
     <pre>
-      ::selection { background: blue; }
-      p.warning   { background:  red; }
+      ::selection          { background: blue; }
+      p.warning::selection { background:  red; }
     </pre>
     and the document included
     <pre>
       &lt;p class="warning">Some &lt;strong>very important information&lt;/strong>&lt;/p>
     </pre>
-    The highlight would be blue around “very important information”
+    The highlight would be blue over “very important information”
     because the <code>&lt;strong></code> element´s ''::selection''
     also matches the ''::selection { background: blue; }'' rule.
     (Remember that ''*'' is implied when a tag selector is missing.)
-    The style rules that would give the intended behavior are
+    The style rules that would give the intended behavior
+    (red highlight within <code>p.warning</code>, blue elsewhere) are
     <pre>
-      :root::selection { background: blue; }
-      p.warning        { background:  red; }
+      :root::selection     { background: blue; }
+      p.warning::selection { background:  red; }
     </pre>
   </div>