community[Qianfan]: add function_call in additional_kwargs (#19550)

- **Description:** add lacked `function_call` field in
`additional_kwargs` in previous version
- **Dependencies:** None of new dependency

libs/community/langchain_community/chat_models/baidu_qianfan_endpoint.py

@@ -65,6 +65,7 @@ def _convert_dict_to_message(_dict: Mapping[str, Any]) -> AIMessage:
             request_id=additional_kwargs["id"],
             object=additional_kwargs.get("object", ""),
             search_info=additional_kwargs.get("search_info", []),
+            function_call=additional_kwargs.get("function_call", {}),
         ),
     )