NixOS/auto-upgrade: add git to service path

Resolves https://github.com/NixOS/nixpkgs/issues/54946
where nixos-rebuild can not find git, when executed
from inside the systemd service

nixos/modules/tasks/auto-upgrade.nix

@@ -78,7 +78,7 @@ let cfg = config.system.autoUpgrade; in
           HOME = "/root";
         } // config.networking.proxy.envVars;
 
-      path = [ pkgs.gnutar pkgs.xz.bin config.nix.package.out ];
+      path = [ pkgs.gnutar pkgs.xz.bin pkgs.gitMinimal config.nix.package.out ];
 
       script = ''
         ${config.system.build.nixos-rebuild}/bin/nixos-rebuild switch ${toString cfg.flags}