Remove flaky expectations for event_order_loadstart_progress.html

No new failures since the speculative fix was committed.

BUG=333880

Review URL: https://codereview.chromium.org/212763007

git-svn-id: svn://svn.chromium.org/blink/trunk@170321 bbb929c8-8fbe-4397-9dbb-9b2b20218538