Update Pixel_DirectComposition_ComplexOverlays flaky expectation for win10 only

This flaky expectation overrode the previous expectation that skips this test
on win7, causing it to start running and failing on Win7 nvidia devices.

TBR=zmo@chromium.org

Bug: 929425, 937545
Change-Id: I724793153e6899c58f3475d368eef0a715b6fa06
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1514974
Reviewed-by: Geoff Lang <geofflang@chromium.org>
Reviewed-by: Zhenyao Mo <zmo@chromium.org>
Commit-Queue: Geoff Lang <geofflang@chromium.org>
Cr-Commit-Position: refs/heads/master@{#639561}
1 file changed