Remove `status` and `traceback` from completion response on the server

[yixu34]

We removed this from our internal version (we'll be moving to public repo-first development soon!), we just need to remove from the public repo too:

llm-engine/server/llm_engine_server/common/dtos/llms.py

Lines 117 to 119 in b2588ea

	status: TaskStatus
	outputs: List[CompletionOutput]
	traceback: Optional[str] = None

[saiatmakuri]

Done as part of #214