nixos/pantheon: switch to xdg.icons.enable

nixos/modules/services/x11/desktop-managers/pantheon.nix

@@ -183,7 +183,6 @@ in
         gnome-menus
         gnome.adwaita-icon-theme
         gtk3.out
-        hicolor-icon-theme
         onboard
         qgnomeplatform
         sound-theme-freedesktop
@@ -224,6 +223,7 @@ in
       environment.etc."gtk-3.0/settings.ini".source = "${pkgs.pantheon.elementary-default-settings}/etc/gtk-3.0/settings.ini";
 
       xdg.mime.enable = true;
+      xdg.icons.enable = true;
 
       xdg.portal.enable = true;
       xdg.portal.extraPortals = with pkgs.pantheon; [