Disables flaky test_rand_quantization (#29463)
Summary:
See https://github.com/pytorch/pytorch/issues/28550.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/29463
Differential Revision: D18405669
Pulled By: mruberry
fbshipit-source-id: 2984c3896a9260a06fbf052afb06e0cb8d28b53d
