Revert "Disable webgl-compressed-texture-etc.html webgl-conformance test on CrOS"

This reverts commit d8b85fc3.

Reason for revert: The original bug has been fixed.

Original change's description:
> Disable webgl-compressed-texture-etc.html webgl-conformance test on CrOS
> 
> The test is failing on CrOS and blocking LKGM updates. This disables it
> while we figure out what regressed to allow for LKGM updates.
> 
> Bug: 1127052
> Change-Id: Ie44baff4b78e495c1af42b4f01e4b6bb6b16071d
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2404749
> Commit-Queue: Ben Pastene <bpastene@chromium.org>
> Reviewed-by: Kenneth Russell <kbr@chromium.org>
> Reviewed-by: Mitsuru Oshima (Slow: gardener) <oshima@chromium.org>
> Reviewed-by: Yuly Novikov <ynovikov@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#806261}

TBR=oshima@chromium.org,ynovikov@chromium.org,kbr@chromium.org,bsheedy@chromium.org,bpastene@chromium.org

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

Bug: 1127052
Change-Id: I346f6a9d5f2149c444d955997975a94bc2abe80e
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2421436Reviewed-by: Brian Sheedy <bsheedy@chromium.org>
Reviewed-by: Mitsuru Oshima <oshima@chromium.org>
Commit-Queue: Lepton Wu <lepton@chromium.org>
Cr-Commit-Position: refs/heads/master@{#809146}

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

@@ -717,7 +717,6 @@ crbug.com/957807 [ chromeos ] deqp/data/gles2/shaders/swizzles.html [ Skip ]
 crbug.com/1043953 [ chromeos ] conformance/textures/misc/texture-size-limit.html [ RetryOnFailure ]
 
 crbug.com/1081973 [ chromeos ] conformance/textures/misc/compressed-tex-image.html [ Failure ]
-crbug.com/1127052 [ chromeos ] conformance/extensions/webgl-compressed-texture-etc.html [ Failure ]
 
 # ChromeOS: AMD
 crbug.com/995652 [ chromeos amd ] conformance/uniforms/out-of-bounds-uniform-array-access.html [ Skip ]