Remove pixel test suppressions now that they've been rebaselined

The rebaseline request was landed in https://codereview.chromium.org/2573803002/ (Bump CSSFilterEffects pixel test revision number to force rebaseline)

BUG=672527
CQ_INCLUDE_TRYBOTS=master.tryserver.chromium.linux:linux_optional_gpu_tests_rel;master.tryserver.chromium.mac:mac_optional_gpu_tests_rel;master.tryserver.chromium.win:win_optional_gpu_tests_rel;master.tryserver.chromium.android:android_optional_gpu_tests_rel

Review-Url: https://codereview.chromium.org/2588793002
Cr-Commit-Position: refs/heads/master@{#439794}

content/test/gpu/gpu_tests/pixel_expectations.py

@@ -12,10 +12,6 @@ class PixelExpectations(GpuTestExpectations):
     # self.Fail('Pixel_Canvas2DRedBox',
     #     ['mac', 'amd', ('nvidia', 0x1234)], bug=123)
 
-    # TODO(robertphillips) remove once rebaselines are complete
-    self.Fail('Pixel_CSSFilterEffects', bug=672527)
-    self.Fail('Pixel_CSSFilterEffects_NoOverlays', bug=672527)
-
     # Software compositing is not supported on Android; so we skip these tests
     # that disables gpu compositing on Android platforms.
     self.Skip('Pixel_OffscreenCanvasUnaccelerated2D', ['android'])