godot_4: remove Twey from maintainers

I haven't maintained this package in many years, nor do I use it
currently, so I'm not best placed to maintain it. @shiryel wrote the
package for Godot 4, which works quite differently.

pkgs/development/tools/godot/4/default.nix

···
     description = "Free and Open Source 2D and 3D game engine";
     license = licenses.mit;
     platforms = [ "i686-linux" "x86_64-linux" "aarch64-linux" ];
-    maintainers = with maintainers; [ twey shiryel ];
+    maintainers = with maintainers; [ shiryel ];
     mainProgram = "godot4";
   };
 }