Make the attr() grammar notation more consistent.

Author: tabatkins

css3-values/Overview.html

@@ -1627,7 +1627,7 @@ <h3 id=attr-notation><span class=secno>8.3. </span> Attribute References:
   <p>The new syntax for the &lsquo;<a href="#attr"><code
    class=css>attr()</code></a>&rsquo; expression is:
 
-  <pre>'attr(' &lt;attr-name> &lt;type-or-unit>? [ ',' &lt;fallback> ]? ')'</pre>
+  <pre>attr( &lt;attr-name> &lt;type-or-unit>? [ , &lt;fallback> ]? )</pre>
 
   <p> where &lt;attr-name> is a <a
    href="http://dev.w3.org/csswg/css3-namespace/#css-qnames">CSS qualified

css3-values/Overview.src.html

@@ -1136,7 +1136,7 @@ <h3 id="attr-notation">
 
 	<p>The new syntax for the ''attr()'' expression is:</p>
 
-	<pre>'attr(' &lt;attr-name> &lt;type-or-unit>? [ ',' &lt;fallback> ]? ')'</pre>
+	<pre>attr( &lt;attr-name> &lt;type-or-unit>? [ , &lt;fallback> ]? )</pre>
 
 	<p>
 		where &lt;attr-name> is a <a href="http://dev.w3.org/csswg/css3-namespace/#css-qnames">CSS qualified name</a>