Remove v1 (#5220)

### What problem does this PR solve?

#5201

### Type of change

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

rag/llm/chat_model.py

     def __init__(self, key, model_name, base_url):
         if not base_url:
             raise ValueError("url cannot be None")
-        if base_url.split("/")[-1] != "v1":
-            base_url = os.path.join(base_url, "v1")
         model_name = model_name.split("___")[0]
         super().__init__(key, model_name, base_url)