Web Animations CSS: Update expectations for tests that now pass

This updates expectations for virtual/threaded/animations and
virtual/threaded/transitions tests that were previously flaky but
now pass.

TBR=dstockwell
BUG=322272

Review URL: https://codereview.chromium.org/112803003

git-svn-id: svn://svn.chromium.org/blink/trunk@163711 bbb929c8-8fbe-4397-9dbb-9b2b20218538