Remove stale screenshot_sync expectations

Removes expectations for the screenshot_sync suite that have been
determined to be stale. This only touches expectations that have passed
100% of the time on all builders.

Bug: 599776, 639489, 978492, 648369, 986939
Bug: 1006045, 1155766
Change-Id: I00b3aec492004c9bbb474d42667fcde5fb51b976
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2593970Reviewed-by: Yuly Novikov <ynovikov@chromium.org>
Commit-Queue: Yuly Novikov <ynovikov@chromium.org>
Auto-Submit: Brian Sheedy <bsheedy@chromium.org>
Cr-Commit-Position: refs/heads/master@{#837925}

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

@@ -56,20 +56,3 @@
 # results: [ Failure RetryOnFailure Skip ]
 # END TAG HEADER
 
-crbug.com/599776 [ win amd ] ScreenshotSync_GPURasterWithCanvas [ RetryOnFailure ]
-crbug.com/599776 [ mac intel ] ScreenshotSync_GPURasterWithCanvas [ RetryOnFailure ]
-crbug.com/599776 [ mac intel ] ScreenshotSync_GPURasterWithDivs [ RetryOnFailure ]
-crbug.com/639489 [ win amd-0x6613 ] ScreenshotSync_GPURasterWithDivs [ Failure ]
-crbug.com/978492 [ mac amd ] ScreenshotSync_GPURasterWithDivs [ RetryOnFailure ]
-crbug.com/978492 [ mac amd ] ScreenshotSync_SWRasterWithCanvas [ RetryOnFailure ]
-
-# TODO(kbr): flakily timing out on this configuration.
-crbug.com/648369 [ linux debug intel ] * [ RetryOnFailure ]
-
-# Flakily getting a WebSocketException on Windows w/ Intel UHD 630
-crbug.com/986939 [ win intel-0x3e92 ] ScreenshotSync_GPURasterWithCanvas [ RetryOnFailure ]
-
-crbug.com/1006045 [ android android-nexus-5x skia-renderer-gl ] ScreenshotSync_GPURasterWithCanvas [ Failure ]
-crbug.com/1006045 [ android android-nexus-5x skia-renderer-gl ] ScreenshotSync_GPURasterWithDivs [ Failure ]
-crbug.com/1006045 [ android android-nexus-5x skia-renderer-gl ] ScreenshotSync_SWRasterWithCanvas [ Failure ]
-crbug.com/1006045 [ android android-nexus-5x skia-renderer-gl ] ScreenshotSync_SWRasterWithDivs [ Failure ]