chromeperf: fix flaky find_change_points test
chromeperf: fix flaky find_change_points test

Extend the range of short sequence tests in find_change_points_test to
reduce flakiness.

R=abennetts@google.com, 34a37f59e4ade3cf49221306f04217acf3e86255@chromium.org

Change-Id: I968f9007763ea8a7ff97b71ef47085252ca50cc9
Reviewed-on: https://chromium-review.googlesource.com/c/catapult/+/2794053
Auto-Submit: Chenlin Fan <ade7e59805b81f027d537665b2c12c1956198b97@chromium.org>
Commit-Queue: Chenlin Fan <ade7e59805b81f027d537665b2c12c1956198b97@chromium.org>
Reviewed-by: Dean Berris <34a37f59e4ade3cf49221306f04217acf3e86255@chromium.org>

catapult-project/catapult,catapult-project/catapult,catapult-project/catapult,catapult-project/catapult,catapult-project/catapult,catapult-project/catapult,catapult-project/catapult