nixos-generate-config: Use the Firefox module (#287614)

nixos/modules/installer/tools/tools.nix

@@ -106,11 +106,12 @@ let
       #   isNormalUser = true;
       #   extraGroups = [ "wheel" ]; # Enable ‘sudo’ for the user.
       #   packages = with pkgs; [
-      #     firefox
       #     tree
       #   ];
       # };
 
+      # programs.firefox.enable = true;
+
       # List packages installed in system profile. To search, run:
       # \$ nix search wget
       # environment.systemPackages = with pkgs; [