Revert "bump hf transformers"

This reverts commit 7f75440.

requirements-common.txt

@@ -5,7 +5,7 @@ sentencepiece  # Required for LLaMA tokenizer.
 numpy
 requests
 py-cpuinfo
-transformers >= 4.40.0 # Required for Llama 3
+transformers >= 4.39.1  # Required for StarCoder2 & Llava.
 fastapi
 uvicorn[standard]
 pydantic >= 2.0  # Required for OpenAI server.