add RequiresGradCheck (#50392)
Summary:
This change improves perf by 3-4% on fastrnns.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/50392
Reviewed By: izdeby
Differential Revision: D25891392
Pulled By: Krovatkin
fbshipit-source-id: 44d9b6907d3975742c9d77102fe6a85aab2c08c0
