[css-values-3] Fix link.

Author: tabatkins

css-values/Overview.bs

@@ -472,7 +472,7 @@ Resource Locators: the <<url>> type</h3>
 
 	* For legacy reasons,
 		a <<url>> can be written without quotation marks around the URL itself.
-		This syntax is <a lt="consume a url token" spec=css-syntax>specially-parsed</a>,
+		This syntax is <a lt="consume a url token" spec=css-syntax-3>specially-parsed</a>,
 		and produces a <<url-token>> rather than a <a>function</a> syntactically. [[!CSS3SYN]]
 	* Some CSS contexts, such as ''@import'', allow a <<url>> to be represented by a <<string>> instead.
 		This behaves identically to writing a ''url()'' function containing that string.