nixos/gnome-initial-setup: Remove gnome-welcome-tour service dependency

This has been dropped in GNOME 40:

https://github.com/GNOME/gnome-initial-setup/commit/2bf1bcaa81c8733665cc33be78652969dd07cd9e

nixos/modules/services/desktops/gnome/gnome-initial-setup.nix

@@ -79,7 +79,6 @@ in
     systemd.user.targets."gnome-session".wants = [
       "gnome-initial-setup-copy-worker.service"
       "gnome-initial-setup-first-login.service"
-      "gnome-welcome-tour.service"
     ];
 
     systemd.user.targets."gnome-session@gnome-initial-setup".wants = [