Increase failure threshold for timing based assert (#25867)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/25867
The test can fail if this is run as a stress test. Increase the
threshold to significantly decrease the probability of failure.
ghstack-source-id: 89743661
Test Plan: Tests pass.
Differential Revision: D17266101
fbshipit-source-id: af514eff305783e4a970ac30c3ebdb02fbdcf4c5
