Revert "Suppress pixel tests"

This reverts commit e34160e3.

Reason for revert: The bots no longer appear to be failing these tests.

Original change's description:
> Suppress pixel tests
> 
> Several pixel tests started failing. The cause is unclear and guess
> culprit CLs do not cleanly revert. It is better to skip the tests for
> now while we can investigate.
> 
> TBR=kbr@chromium.org
> 
> Bug: 1102086
> Change-Id: Ib64ec3c68dab713629100226e1eab5628763df65
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2283242
> Reviewed-by: Chris Blume <cblume@chromium.org>
> Commit-Queue: Chris Blume <cblume@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#785392}

TBR=cblume@chromium.org

# Not skipping CQ checks because original CL landed > 1 day ago.

Bug: 1102086
Change-Id: I56055436a7c1c13d83baeb7f1806cda8958a295f
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2292798Reviewed-by: Chris Blume <cblume@chromium.org>
Reviewed-by: Kenneth Russell <kbr@chromium.org>
Commit-Queue: Chris Blume <cblume@chromium.org>
Cr-Commit-Position: refs/heads/master@{#787592}

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

@@ -331,13 +331,3 @@ crbug.com/1086690 [ chromeos ] Pixel_WebGLSadCanvas [ Skip ]
 
 # Likely produces a Dawn validation errors that makes rendering skipped.
 crbug.com/1097735 [ use-skia-dawn ] Pixel_PaintWorkletTransform [ Failure ]
-
-# TODO(cblume): temporarily suppress these test until reverted / fixed.
-crbug.com/1102086 [ win7 amd no-use-skia-dawn no-skia-renderer ] Pixel_Video_MP4_FourColors_Aspect_4x3 [ Skip ]
-crbug.com/1102086 [ mac intel ] Pixel_Video_Context_Loss_MP4 [ Skip ]
-crbug.com/1102086 [ mac intel no-use-skia-dawn no-skia-renderer ] Pixel_Video_MP4 [ Skip ]
-crbug.com/1102086 [ mac intel no-use-skia-dawn no-skia-renderer ] Pixel_Video_MP4_FourColors_Aspect_4x3 [ Skip ]
-crbug.com/1102086 [ mac intel no-use-skia-dawn no-skia-renderer ] Pixel_Video_MP4_FourColors_Rot_180 [ Skip ]
-crbug.com/1102086 [ mac intel no-use-skia-dawn no-skia-renderer ] Pixel_Video_MP4_FourColors_Rot_270 [ Skip ]
-crbug.com/1102086 [ mac intel no-use-skia-dawn no-skia-renderer ] Pixel_Video_MP4_FourColors_Rot_90 [ Skip ]
-crbug.com/1102086 [ mac intel ] Pixel_Video_MP4_Rounded_Corner [ Skip ]