Removing pad-gesture-fling from TestExpectations.

Looks like r164581 fixed the flakiness issues.

BUG=261277

Review URL: https://codereview.chromium.org/130053002

git-svn-id: svn://svn.chromium.org/blink/trunk@164798 bbb929c8-8fbe-4397-9dbb-9b2b20218538