[css-backgrounds-4] Missing closing PRE (#5942)

Author: nschonni

css-backgrounds-4/Overview.bs

@@ -397,7 +397,7 @@ Partial Borders: the 'border-limit' property</h3>
 		<p>The following example draws only the curved parts of the corners.</p>
 		<pre>box { border: solid; border-radius: 1em 2em; border-parts: corners; }</pre>
 		<p>The following example draws only the left 4em of the top border.</p>
-		<pre>box { border-top: solid; border-parts: left 4em; }
+		<pre>box { border-top: solid; border-parts: left 4em; }</pre>
 		<p>The following example draws only the first 10px of each corner:</p>
 		<pre>box { border: solid; border-parts: corners 10px; }</pre>
 		<p>The following example draws the curved part of the corner plus 5px