caffe2: remove support for specifically running "flaky tests" (#112007)
Summary:
In March 2019 D14468816 introduced some infra to mark tests as flaky
while still running them. In July 2019 D15797371 removed the last use of this
feature. Remove the related code as well.
Test Plan: ci
Reviewed By: mlogachev
Differential Revision: D50601204
Pull Request resolved: https://github.com/pytorch/pytorch/pull/112007
Approved by: https://github.com/malfet
