elasticsearch-curator: add top-level package using older click

See https://github.com/NixOS/nixpkgs/pull/58023 for a discussion
of why this is necessary. The upstream issue can be found at
https://github.com/elastic/curator/pull/1280.

nixos/modules/services/search/elasticsearch-curator.nix

@@ -86,7 +86,7 @@ in {
       startAt = cfg.interval;
       serviceConfig = {
         ExecStart =
-          "${pkgs.python3Packages.elasticsearch-curator}/bin/curator" +
+          "${pkgs.elasticsearch-curator}/bin/curator" +
           " --config ${curatorConfig} ${curatorAction}";
       };
     };