nixos/privatebin: fix defaultText

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

@@ -52,7 +52,7 @@ in
     group = lib.mkOption {
       type = lib.types.str;
       default = if cfg.enableNginx then "nginx" else defaultGroup;
-      defaultText = "If `services.privatebin.enableNginx` is true then `nginx` else ${defaultGroup}";
+      defaultText = lib.literalExpression "if config.services.privatebin.enableNginx then \"nginx\" else \"${defaultGroup}\"";
       description = ''
         Group under which privatebin runs. It is best to set this to the group
         of whatever webserver is being used as the frontend.
@@ -139,7 +139,6 @@ in
   };
 
   config = lib.mkIf cfg.enable {
-
     services.privatebin.settings = {
       main = lib.mkDefault { };
       model.class = lib.mkDefault "Filesystem";