[Sheriff] Disable flaky test:...

[Sheriff] Disable flaky test: http/tests/credentialmanager/credentialscontainer-get-with-virtual-authenticator.html

TBR=tommili@chromium.org

Bug: 1010863
Change-Id: Ia3bccb6f13cd1892028494fa6f742f39cde8a4da
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1841755Reviewed-by: Samuel Huang <huangs@chromium.org>
Commit-Queue: Samuel Huang <huangs@chromium.org>
Cr-Commit-Position: refs/heads/master@{#702989}

third_party/blink/web_tests/TestExpectations

@@ -6186,3 +6186,4 @@ crbug.com/1010657 [ Mac ] virtual/disable-deferred-rendering/fast/canvas/image-o
 # Sheriff 2019-10-04
 crbug.com/1011191 [ Mac ] paint/invalidation/svg/use-clipped-hit.svg  [ Pass Failure ]
 crbug.com/1011188 [ Mac ] paint/invalidation/svg/svg-background-partial-redraw.html [ Pass Failure ]
+crbug.com/1010863 http/tests/credentialmanager/credentialscontainer-get-with-virtual-authenticator.html [ Skip ]