Replace <section> with <article> in markup example

I left out classes as those are not really relevant and their choosing would be *opinionated*.

Author: thierryk

css-contain/Overview.bs

@@ -115,19 +115,20 @@ Strong Containment: the 'contain' property</h2>
 
 		<pre class='lang-css'>
 			&lt;body>
-				&lt;aside class='sidebar'>...&lt;/aside>
-				&lt;article class='messages'>
-					&lt;section class='message'>
+				&lt;aside>...&lt;/aside>
+				&lt;section>
+					&lt;h2>Messages&lt;/h2>				
+					&lt;article>
 						Lol, check out this dog: images.example.com/jsK3jkl
-					&lt;/section>
-					&lt;section class='message'>
+					&lt;/article>
+					&lt;article>
 						I had a ham sandwich today. #goodtimes
-					&lt;/section>
-					&lt;section class='message'>
+					&lt;/article>
+					&lt;article>
 						I have political opinions that you need to hear!
-					&lt;/section>
+					&lt;/article>
 					…
-				&lt;/article>
+				&lt;/section>
 			&lt;/body>
 		</pre>