[nit] fix some typo within documentation (#40692)
Summary:
Apologize if this seems trivial, but i'd like to fix them on my way of reading some of the source code. Thanks!
Pull Request resolved: https://github.com/pytorch/pytorch/pull/40692
Differential Revision: D22284651
Pulled By: mrshenli
fbshipit-source-id: 4259d1808aa4d15a02cfd486cfb44dd75fdc58f8
