[css-values] Fix broken quoting in changes section.

Author: dbaron

css-values/Overview.bs

@@ -2300,7 +2300,7 @@ Changes</h2>
 	Changes since <a href="http://www.w3.org/TR/css-values-3/">Level 3</a>:
 
 	<ul>
-		<li>Added the ''vi'', ''vb'', ''ic'', ''lh' and ''rlh'' units.
+		<li>Added the ''vi'', ''vb'', ''ic'', ''lh'' and ''rlh'' units.
 	</ul>
 
 <h2 class="no-num" id="sec-pri">