fix classname li.current_page_ancestor

It was li.current-page-ancestor before. wordpress uses li.current_page_ancestor

library/less/_481up.less

@@ -61,7 +61,7 @@ NAVIGATION STYLES
 			/* highlight current page */
 			li.current-menu-item, 
 			li.current_page_item,
-			li.current-page-ancestor {
+			li.current_page_ancestor {
 				a {}
 			}  /* end current highlighters */
 		} /* end .menu ul */