With that we can also enable the tests DifferentStencilMasksTest.*

Bug: angleproject:5851
Change-Id: If2c992e456716f606320e3992f389823d0af050f
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2853584
Commit-Queue: Gert Wollny <gert.wollny@collabora.com>
Reviewed-by: Cody Northrop <cnorthrop@google.com>
Reviewed-by: Jamie Madill <jmadill@chromium.org>