{
  services.xserver.enable = true;
  services.xserver.displayManager.gdm.enable = true;
  services.xserver.desktopManager.gnome3.enable = true;
}

{
  services.xserver.enable = true;
  services.xserver.displayManager.gdm.enable = true;
  services.xserver.desktopManager.gnome.enable = true;
}

Use new gnome desktop manager option
fix(nixos/sys): Use new gnome desktop manager option

As the old one was deprecated from NixOS 21.05.
