Revert "Exposing native _scaled_dot_product_attention to torch.nn (#85044)"
This reverts commit 9fdd8a8b7f171be70ea3bd4724c38852ef292d73.
Reverted https://github.com/pytorch/pytorch/pull/85044 on behalf of https://github.com/huydhn due to This breaks CUDA 10.2 in trunk. We are deprecating CUDA 10.2, but it is still here in the mean time
