Remove unused global reference. props ampt. fixes #20863.

git-svn-id: https://develop.svn.wordpress.org/trunk@21252 602fd350-edb4-49c9-b593-d223f7449a82

wp-includes/nav-menu-template.php

@@ -65,7 +65,6 @@ class Walker_Nav_Menu extends Walker {
 	 * @param object $args
 	 */
 	function start_el( &$output, $item, $depth = 0, $args = array(), $id = 0 ) {
-		global $wp_query;
 		$indent = ( $depth ) ? str_repeat( "\t", $depth ) : '';
 
 		$class_names = $value = '';