Drop timeout for video-object-fit-* tests.

These timeouts cause a lot of flakiness on the bot and on my local machine when I run the test alone. We should rely on the test infrastructure to catch the timeout, instead of create our own timeout limit, which by no means could be accurate.

The test was flaky on bots due to these timeouts:
http://test-results.appspot.com/dashboards/flakiness_dashboard.html#group=%40ToT%20Blink&tests=video-object-fit-stable.html

BUG=282484
TEST=This CL fixes flakiness.

Review URL: https://chromiumcodereview.appspot.com/23645017

git-svn-id: svn://svn.chromium.org/blink/trunk@158075 bbb929c8-8fbe-4397-9dbb-9b2b20218538