Revert "Introduce CUDA-only `_scaled_mm` op (#106844)"
This reverts commit 9440a8cbec52ce5c2eb9b95b4a8d9f16055d611d.
Reverted https://github.com/pytorch/pytorch/pull/106844 on behalf of https://github.com/izaitsevfb due to Breaks internal builds ([comment](https://github.com/pytorch/pytorch/pull/106844#issuecomment-1679858327))
