Revert "NestedTensor Softmax (#83435)"
This reverts commit d7fc76a1ed33a155c8be795abe67315a4459e1a0.
Reverted https://github.com/pytorch/pytorch/pull/83435 on behalf of https://github.com/huydhn due to This is suspected to break functorch tests in trunk https://hud.pytorch.org/pytorch/pytorch/commit/d7fc76a1ed33a155c8be795abe67315a4459e1a0
