Disable test_backward_per_tensor in test_fake_quant (#30594)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/30594
This testcase started breaking, clean up for the build.
ghstack-source-id: 94736837
Test Plan: Unittest disabling change
Differential Revision: D18758635
fbshipit-source-id: 05df1158ff0ccd75e401f352da529fb663b1cae0
