WindowServer: Add IPC call to remove a menu's item

Author: https://github.com/mrkct
Commit: 8ede1a6a6f
Pull-request: https://github.com/SerenityOS/serenity/pull/12519
Reviewed-by: https://github.com/itamar8910 ✅

Userland/Services/WindowServer/Menu.h

@@ -97,6 +97,7 @@ public:
     const Gfx::Font& font() const;
 
     MenuItem* item_with_identifier(unsigned);
+    bool remove_item_with_identifier(unsigned);
     void redraw();
     void redraw(MenuItem const&);