fix lint error

nebuly/providers/langchain.py

@@ -484,7 +484,7 @@ def on_llm_end(  # pylint: disable=arguments-differ
         **kwargs: Any,
     ) -> None:
         if self.verbose:
-            logger.info(f"LLM model ended")
+            logger.info("LLM model ended")
         self._events_storage.events[run_id].data.add_end_event_data(
             kwargs=kwargs, output=response
         )