[css-variables] Markup typo

Author: tabatkins

css-variables/Overview.html

@@ -589,7 +589,7 @@ <h2 id=using-variables><span class=secno>3. </span> Using Cascading
     can supply defaults, so the app author only needs to supply values for
     the variables they wish to override.
 
-   <pre class=example>/* In the component's style: */
+   <pre>/* In the component's style: */
 .component .header { 
   color: var(header-color, blue); 
 }

css-variables/Overview.src.html

@@ -370,7 +370,7 @@ <h2 id='using-variables'>
 		With fallback, the component author can supply defaults,
 		so the app author only needs to supply values for the variables they wish to override.
 
-		<pre class='example'>
+		<pre>
 		/* In the component's style: */
 		.component .header { 
 			color: var(header-color, blue);