typo (#48887)
Summary:
a small grammar fix
jspisak - thank you!
Pull Request resolved: https://github.com/pytorch/pytorch/pull/48887
Reviewed By: malfet, zhangguanheng66
Differential Revision: D25358638
Pulled By: brianjo
fbshipit-source-id: 3b805b54df3410f8770e1c6ddc569b26661cece4
