nixos/gnome: enable ibus to fix keyboard handling

GNOME 49 (via GTK4 and Wayland) depends on ibus. Add it to keep having
working dead keys functionality like before.

Fixes https://github.com/nixos/nixpkgs/issues/464473.

nixos/modules/services/desktop-managers/gnome.nix

@@ -320,6 +320,8 @@ in
 
     (lib.mkIf serviceCfg.core-os-services.enable {
       hardware.bluetooth.enable = mkDefault true;
+      i18n.inputMethod.enable = mkDefault true;
+      i18n.inputMethod.type = mkDefault "ibus";
       programs.dconf.enable = true;
       security.polkit.enable = true;
       security.rtkit.enable = mkDefault true;