This test is flaky on the metal backend.

Bug: angleproject:5713
Change-Id: I1d789825e0322f00b017a60f8fd1cef02b5b3088
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2732787
Commit-Queue: Jonah Ryan-Davis <jonahr@google.com>
Commit-Queue: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Jamie Madill <jmadill@chromium.org>