Revert "Add scalar conversion using avx instructions for half (#102140)"
This reverts commit 888bdddb1ed0f3bfbbfc964f3b6080b0ea431dfd.
Reverted https://github.com/pytorch/pytorch/pull/102140 on behalf of https://github.com/jeanschmidt due to This is breaking internal tests @cpuhrsch can share more context and help with a follow up ([comment](https://github.com/pytorch/pytorch/pull/102140#issuecomment-1660686075))
