add hf_transfer to requirements.txt (vllm-project#3031)

Dockerfile

@@ -96,7 +96,7 @@ RUN --mount=type=cache,target=/root/.cache/pip \
 FROM vllm-base AS vllm-openai
 # install additional dependencies for openai api server
 RUN --mount=type=cache,target=/root/.cache/pip \
-    pip install accelerate
+    pip install accelerate hf_transfer
 
 COPY --from=build /workspace/vllm/*.so /workspace/vllm/
 COPY vllm vllm