Pixel tests: suppress failing Skia Dawn test.

This test is likely failing because Skia triggers newly added Dawn
validation.

TBR=bajones@chromium.org

Bug: chromium:1097735
Change-Id: If5e6411edd97e9b279aa0905b60c383b6827e608
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2255364Reviewed-by: Corentin Wallez <cwallez@chromium.org>
Commit-Queue: Corentin Wallez <cwallez@chromium.org>
Cr-Commit-Position: refs/heads/master@{#780769}

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

@@ -330,3 +330,6 @@ crbug.com/1086687 [ chromeos chromeos-board-kevin ] Pixel_PrecisionRoundedCorner
 
 # Produces blank images on gpu-fyi-try-chromeos-kevin, gpu-fyi-try-chromeos-amd64-generic.
 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 ]