Capture/Replay: Mark another ImageTest test as FLAKY Bug: angleproject:6286 Change-Id: Idbbdab532a449d754d05208aeadd94462c8c572a Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/3276041 Reviewed-by: Cody Northrop <cnorthrop@google.com> Commit-Queue: Shahbaz Youssefi <syoussefi@chromium.org>