[css-conditional] Autolink to definition of support, to fix bikeshed warning.

Author: dbaron

css-conditional-3/Overview.bs

@@ -403,7 +403,7 @@ follows:</p>
 
 <dt>supports_declaration_condition</dt>
 <dd>
-  The result is whether the CSS processor <a href="#support-definition">supports</a> the declaration
+  The result is whether the CSS processor <a>supports</a> the declaration
   within the parentheses.
 </dd>