Disable flaky TestMomentumSGD.test_fp16momentum_sgd (#31369)
Summary:
Related to https://github.com/pytorch/pytorch/issues/31368
Pull Request resolved: https://github.com/pytorch/pytorch/pull/31369
Differential Revision: D19147072
Pulled By: VitalyFedyunin
fbshipit-source-id: 6fad13be7b35f992d84a20f23877cad05ff18616
