Supress RobustResourceInitTestES3.MaskedStencilClearBuffer on Linux OpenGL This test flakes on many platforms. BUG=angleproject:2408 BUG=angleproject:2407 Change-Id: I9e8ff8aedc02962656c1a336c3f34191920ae8c7 Reviewed-on: https://chromium-review.googlesource.com/c/1352222 Commit-Queue: Geoff Lang <geofflang@chromium.org> Reviewed-by: Geoff Lang <geofflang@chromium.org> Reviewed-by: Jamie Madill <jmadill@chromium.org>