nixos/garage: allow all available log levels in cfg.logLevel

`error` and `warn` have always been valid log levels.
But because the upstream docs never mentioned those, we simply didn't
add them to the enum of our module option.

The upstream docs have been updated and now mention `error` and `warn`
as well.

Upstream PR: https://git.deuxfleurs.fr/Deuxfleurs/garage/pulls/716

nixos/modules/services/web-servers/garage.nix

@@ -30,7 +30,7 @@ in
     };
 
     logLevel = mkOption {
-      type = types.enum ([ "info" "debug" "trace" ]);
+      type = types.enum ([ "error" "warn" "info" "debug" "trace" ]);
       default = "info";
       example = "debug";
       description = lib.mdDoc "Garage log level, see <https://garagehq.deuxfleurs.fr/documentation/quick-start/#launching-the-garage-server> for examples.";