Beef up comment in AccumulateType (#63503)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/63503
Signed-off-by: Edward Z. Yang <ezyang@fb.com>
Test Plan: Imported from OSS
Reviewed By: ngimel
Differential Revision: D30403160
Pulled By: ezyang
fbshipit-source-id: 6cb24418152d9fb146f86b6f973ec50f1a397a58
