Optimize backward for torch.repeat (#46726)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/46726
Fixes #43192
Test Plan: Imported from OSS
Reviewed By: heitorschueroff
Differential Revision: D24739840
Pulled By: ejguan
fbshipit-source-id: ddf21fc52c4676de25ad7bfb0b5c1c23daa77ee6
