clarify default value of requires_grad for tensors (#61038)
Summary: Pull Request resolved: https://github.com/pytorch/pytorch/pull/61038
Test Plan: Imported from OSS
Reviewed By: albanD
Differential Revision: D29491984
Pulled By: dagitses
fbshipit-source-id: 7e6b7f8e81d77f38c881b86a68c17d3cf5483dad
