gitlab: fix archive urls for gitlab service

Accessing an url like https://gitlab.example.org/group/project/repository/archive.tar.gz?ref=master
requires tar/gzip to be in the path of the gitlab-workhorse service otherwise it fails.

nixos/modules/services/misc/gitlab.nix

@@ -439,6 +439,8 @@ in {
       environment.GITLAB_SHELL_CONFIG_PATH = gitlabEnv.GITLAB_SHELL_CONFIG_PATH;
       path = with pkgs; [
         gitAndTools.git
+        gnutar
+        gzip
         openssh
         gitlab-workhorse
       ];