Remove VS2017 workaround for autocasting (#42352)
Summary:
Because VS2017 is no longer supported after https://github.com/pytorch/pytorch/pull/42144
cc: mcarilli
Pull Request resolved: https://github.com/pytorch/pytorch/pull/42352
Reviewed By: malfet
Differential Revision: D22962809
Pulled By: ngimel
fbshipit-source-id: 0346cde87bf5d617dfc0d7b34c92ac6ec5bbf568
