Remove the closed event of Menu

The callback of Menu.popup does more things, and there is actually no
request for the closed event.

lib/browser/api/menu.js

@@ -39,9 +39,6 @@ Menu.prototype._init = function () {
         const found = this.groupsMap[id].find(item => item.checked) || null
         if (!found) v8Util.setHiddenValue(this.groupsMap[id][0], 'checked', true)
       }
-    },
-    menuClosed: () => {
-      this.emit('closed')
     }
   }
 }