graphics.Clvk: remove stoney expectation

Timer issues have been fixed by crrev/c/4593881. Then stoney was still
failing on unmap race condition issues that have been fixed by clvk
uprev to r46.

It is now passing all the time, thus removing the expectation for it.

BUG=b:292394393
TEST=CI

Change-Id: Ibc18892fe982da7662cd37d0af55a1f7aeb052fb
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/graphics/+/4821547
Commit-Queue: Ilja Friedel <ihf@chromium.org>
Tested-by: Romaric Jodin <rjodin@chromium.org>
Reviewed-by: Ilja Friedel <ihf@chromium.org>