Fix typo (#45379)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/45379
Registeres -> Registers in reducer.h.
ghstack-source-id: 112982279
Test Plan: N/A
Reviewed By: mrshenli
Differential Revision: D23951203
fbshipit-source-id: 96c7dc2e1e12c132339b9ac83ce1da52c812740c
