build(deps): remove unused hf-transfer dependency (#338)

hf-transfer is declared in pyproject.toml but never activated: nothing in
the codebase sets HF_HUB_ENABLE_HF_TRANSFER, and downloads go through
from_pretrained / hf_hub_download with no transfer toggle. huggingface-hub
is pinned ~=1.7, where Xet is the default transfer backend, so hf-transfer
is dead weight and only surfaces a deprecation warning.

pyproject.toml

@@ -25,7 +25,6 @@ dependencies = [
     "accelerate~=1.13",
     "bitsandbytes~=0.49",
     "datasets~=4.7",
-    "hf-transfer~=0.1",
     "huggingface-hub~=1.7",
     "immutabledict~=4.3",
     "kernels~=0.13",