purge HF_HUB_ENABLE_HF_TRANSFER; promote Xet (#12497)
* purge HF_HUB_ENABLE_HF_TRANSFER; promote Xet
* purge HF_HUB_ENABLE_HF_TRANSFER; promote Xet x2
* restrict docker build test to the ones we actually use in CI.
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Co-authored-by: YiYi Xu <yixu310@gmail.com>
Co-authored-by: Sayak Paul <spsayakpaul@gmail.com>
