fix:api /factories wrong return (#11015)

### What problem does this PR solve?

change:
api /factories wrong return

### Type of change

- [x] Bug Fix (non-breaking change which fixes an issue)

api/utils/api_utils.py

@@ -628,6 +628,6 @@ async def is_strong_enough(chat_model, embedding_model):
 def get_allowed_llm_factories() -> list:
     factories = LLMFactoriesService.get_all()
     if settings.ALLOWED_LLM_FACTORIES is None:
-        return factories
+        return list(factories)
 
     return [factory for factory in factories if factory.name in settings.ALLOWED_LLM_FACTORIES]