dconf module: add dconf to services.dbus.packages

Some programs like eog seem to need dconf accessible on dbus.
Without this change I get

(eog:1738): dconf-WARNING **: 21:20:52.770: failed to commit changes to
dconf: GDBus.Error:org.freedesktop.DBus.Error.ServiceUnknown: The name
ca.desrt.dconf was not provided by any .service files

nixos/modules/programs/dconf.nix

@@ -32,6 +32,8 @@ in
     environment.etc = optionals (cfg.profiles != {})
       (mapAttrsToList mkDconfProfile cfg.profiles);
 
+    services.dbus.packages = [ pkgs.gnome3.dconf ];
+
     environment.variables.GIO_EXTRA_MODULES = optional cfg.enable
       "${pkgs.gnome3.dconf.lib}/lib/gio/modules";
     # https://github.com/NixOS/nixpkgs/pull/31891