nixos/sftpgo: change type of dataDir option to path

The dataDir options describes a path, so it should be an option of type
path.

Author: NetaliDev

nixos/modules/services/web-apps/sftpgo.nix

@@ -35,7 +35,7 @@ in
     };
 
     dataDir = mkOption {
-      type = types.str;
+      type = types.path;
       default = "/var/lib/sftpgo";
       description = ''
         The directory where SFTPGo stores its data files.