Revert "Remove Pixel_CSSFilterEffects_NoOverlays failure expectation"

This reverts commit 7076daa4.

Reason for revert: The test started failing again after this CL was landed. More details on crbug.com/1040202

Original change's description:
> Remove Pixel_CSSFilterEffects_NoOverlays failure expectation
> 
> Test was producing a minor image diff, has been triaged.
> 
> Bug: 1040202
> Change-Id: Iae6dd08ea4b97d7f4975971b8abbb948d97867d5
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1992564
> Reviewed-by: Kenneth Russell <kbr@chromium.org>
> Commit-Queue: Brandon Jones <bajones@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#729597}

TBR=kbr@chromium.org,bajones@chromium.org

Change-Id: Id637b25550ce9f423e448d0b332c0dbbf34b9eb9
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: 1040202
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1992367Reviewed-by: sebsg <sebsg@chromium.org>
Commit-Queue: sebsg <sebsg@chromium.org>
Cr-Commit-Position: refs/heads/master@{#729736}

content/test/gpu/gpu_tests/test_expectations/pixel_expectations.txt

@@ -199,6 +199,9 @@ crbug.com/1033121 [ android skia-renderer use-gl no-use-vulkan ] Pixel_Video_MP4
 # Produces blank images on Intel HD 630 w/ Mesa 19.0.2
 crbug.com/976861 [ linux intel-0x5912 ] Pixel_OffscreenCanvasTransferToImageBitmap [ Skip ]
 
+# Flakes regularly on Mac.
+crbug.com/1040202 [ mac ] Pixel_CSSFilterEffects_NoOverlays [ Failure ]
+
 # Skip swap chain tests on non-Windows
 [ android ] Pixel_CanvasLowLatency2DSwapChain [ Skip ]
 [ android ] Pixel_CanvasLowLatencyWebGLSwapChain [ Skip ]