Re-enable ContextLost_WebGL2Blocked

The root cause of the Intel AMD failures has been addressed.
I'd like to try re-enabling this.

TEST=context_lost tests
     ContextLost_WebGL2Blocked

Bug: 1008125
Change-Id: I96ccdc26e0468a384810530e10c684738699a412
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1934689Reviewed-by: Yuly Novikov <ynovikov@chromium.org>
Commit-Queue: Jonathan Ross <jonross@chromium.org>
Cr-Commit-Position: refs/heads/master@{#718889}

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

 # tags: [ android linux lion mac mountainlion win win7 win8 win10]
 # tags: [ debug ]
-# tags: [ amd-0x6613 nvidia qualcomm-adreno-(tm)-418 qualcomm-adreno-(tm)-420 ]
+# tags: [ nvidia qualcomm-adreno-(tm)-418 qualcomm-adreno-(tm)-420 ]
 # tags: [ asan no-asan ]
 # results: [ Failure RetryOnFailure Skip ]
 
-# Linux AMD R7 240
-crbug.com/1008125 [ linux amd-0x6613 ] ContextLost_WebGL2Blocked [ Skip ]
-
 # Win7 bots
 crbug.com/603329 [ win7 ] ContextLost_WebGLContextLostFromGPUProcessExit [ RetryOnFailure ]