fix ddp logging flaky test (#55414)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/55414
close #55384
backward_compute_comm_overlap_time may not be larger than 1. we should check backward_compute_time, backward_comm_time are larger than 1 instead.
ghstack-source-id: 126360517
Test Plan: unit tests
Reviewed By: H-Huang, SciPioneer
Differential Revision: D27606132
fbshipit-source-id: 418fe9f958287779d637856e355cc36cab384c68
