[Reducer] Move require_finalize_ (#100782)
This doesn't need to be set in the loop, just once.
Differential Revision: [D45632426](https://our.internmc.facebook.com/intern/diff/D45632426/)
Pull Request resolved: https://github.com/pytorch/pytorch/pull/100782
Approved by: https://github.com/Skylion007, https://github.com/fegin
