fix nav breakpoint issue (backports #23528)

Author: bobemoe

lib/web/mage/menu.js

@@ -22,7 +22,7 @@ define([
             showDelay: 42,
             hideDelay: 300,
             delay: 0,
-            mediaBreakpoint: '(max-width: 768px)'
+            mediaBreakpoint: '(max-width: 767px)'
         },
 
         /**