Remove AVX detection code that duplicates FindAVX.cmake (#61748)
Summary:
This PR deletes some code in `MiscCheck.cmake` that perform the exact
same functionality as `FindAVX.cmake`.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/61748
Reviewed By: ejguan
Differential Revision: D29791282
Pulled By: malfet
fbshipit-source-id: 6595fd1b61c8ae12b821fad8c9a34892dd52d213
