Update requirements.txt

[In the `datasets` library version `4.0.0`, `trust_remote_code=True` was removed](https://github.com/LiveCodeBench/LiveCodeBench/issues/108). However, since there is no simple alternative in this case, pin the library version.

requirements.txt

@@ -2,6 +2,6 @@ fastapi
 uvicorn
 python-multipart
 pydantic
-datasets
+datasets==3.6.0
 huggingface_hub
 pandas