Revert "Make grad mode error just a warning (#56401)" (#57640)
Summary:
This reverts commit 63dac82444cc522f177b801d9f0cd2e22417c2f4.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/57640
Reviewed By: soulitzer, yuguo68
Differential Revision: D28223946
Pulled By: albanD
fbshipit-source-id: 641b87cff1e2f08162ca8cacae333105e89438f1
