restore async for in litellm calls

Author: prassanna-ravishankar

src/agentex/lib/core/adapters/llm/adapter_litellm.py

@@ -47,5 +47,5 @@ async def acompletion_stream(
         if not kwargs.get("stream"):
             raise ValueError("To use streaming, please set stream=True in the kwargs")
 
-        async for chunk in llm.acompletion(*args, **kwargs):  # type: ignore[misc]
+        async for chunk in await llm.acompletion(*args, **kwargs):  # type: ignore[misc]
             yield Completion.model_validate(chunk)