core[patch]: Fixed bug in dict to message conversion. (#17023)

- **Description**: We discovered a bug converting dictionaries to
messages where the ChatMessageChunk message type isn't handled. This PR
adds support for that message type.
- **Issue**: #17022 
- **Dependencies**: None
- **Twitter handle**: None

libs/core/langchain_core/messages/__init__.py

@@ -92,6 +92,8 @@ def _message_from_dict(message: dict) -> BaseMessage:
         return ToolMessageChunk(**message["data"])
     elif _type == "SystemMessageChunk":
         return SystemMessageChunk(**message["data"])
+    elif _type == "ChatMessageChunk":
+        return ChatMessageChunk(**message["data"])
     else:
         raise ValueError(f"Got unexpected message type: {_type}")