Removed TestExpectations comments after rebaseline

image-set related flaky Windows tests were commented on TestExpectations, since they needed rebaselining.
Once rebaselined, I've uncommented these tests in TestExpectations.

BUG=299556

Review URL: https://codereview.chromium.org/29163004

git-svn-id: svn://svn.chromium.org/blink/trunk@159991 bbb929c8-8fbe-4397-9dbb-9b2b20218538