fix analysis warning

Author: felangel

bricks/dart_frog_prod_server/hooks/lib/src/create_external_packages_folder.dart

@@ -73,7 +73,7 @@ Future<List<String>> createExternalPackagesFolder({
             externalDependency.path,
             from: buildDirectory.path,
           ),
-        }
+        },
     },
   );