Fix pytest 9 error

Author: pquentin

test_elasticsearch/test_async/test_server/test_rest_api_spec.py

@@ -242,7 +242,7 @@ async def _feature_enabled(self, name):
 
 
 @pytest.fixture(scope="function")
-def async_runner(async_client_factory):
+async def async_runner(async_client_factory):
     return AsyncYamlRunner(async_client_factory)