style: fix line length in fake_chat_models.py

Split long line to comply with max line length of 88 characters.

Author: zhangzhefang-github

libs/core/langchain_core/language_models/fake_chat_models.py

@@ -386,7 +386,9 @@ def _generate(
         run_manager: CallbackManagerForLLMRun | None = None,
         **kwargs: Any,
     ) -> ChatResult:
-        return ChatResult(generations=[ChatGeneration(message=messages[-1])], llm_output={})
+        return ChatResult(
+            generations=[ChatGeneration(message=messages[-1])], llm_output={}
+        )
 
     @property
     def _llm_type(self) -> str: