supertux-editor: mark as broken (#122781)

SuperTux now uses an in-game editor, so there's no point in trying to build this old C# monstrosity.

pkgs/applications/editors/supertux-editor/default.nix

@@ -34,7 +34,7 @@ stdenv.mkDerivation {
     description = "Level editor for SuperTux";
     homepage = "https://github.com/SuperTux/supertux-editor";
     license = licenses.gpl3Plus;
-    maintainers = with maintainers; [ mathnerd314 ];
     platforms = platforms.linux;
+    broken = true;
   };
 }