[css-counter-styles] markup fix

Author: tabatkins

css-counter-styles/Overview.bs

@@ -701,7 +701,7 @@ Building Off Of Existing Counter Styles: the ''extends'' system
 		Rather than writing up an entirely new counter style,
 		this can be done by just extending ''decimal'':
 
-		<pre class='css'>
+		<pre>
 		@counter-style decimal-paren {
 			system: extends decimal;
 			suffix: ") ";

css-counter-styles/Overview.html

@@ -777,7 +777,7 @@ <h4 class="heading settled" data-level=3.1.7 id=extends-system><span class=secno
 <p>Rather than writing up an entirely new counter style,
 		this can be done by just extending <a class=css data-link-type=maybe href=#valuedef-counter-style-name-decimal title=decimal>decimal</a>:</p>
 
-		<pre class=css>@counter-style decimal-paren {
+		<pre>@counter-style decimal-paren {
   system: extends decimal;
   suffix: ") ";
 }