Skip the the test TransformFeedbackTest::EndWithDifferentProgram() on
Vulkan + Pixel 2 since it appears to be flaky.

Test: TransformFeedbackTest::EndWithDifferentProgram()
Bug: chromium:1207380
Change-Id: Iedfe1e96a204eca5954097be9e61820b775eb0b0
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2886358Reviewed-by: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Yuly Novikov <ynovikov@chromium.org>
Commit-Queue: Yuly Novikov <ynovikov@chromium.org>