Apply suggestion from @Copilot

Co-authored-by: Copilot <[email protected]>

Author: CaralHsi

src/memos/llms/deepseek.py

@@ -50,5 +50,4 @@ def generate_stream(self, messages: MessageList, **kwargs) -> Generator[str, Non
                 yield delta.reasoning_content
 
             if hasattr(delta, "content") and delta.content:
-                answer_parts += delta.content
                 yield delta.content