Change testing config for new Query tiles stable experiment

For the new Query Tiles experiment, we need to run preperiod
first for some time. So change the testing config to reflect that.

BUG=1127441

Change-Id: I2a79c15c538178abffe72aebbd352798bb5841d8
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2833682
Reviewed-by: Shakti Sahu <shaktisahu@chromium.org>
Commit-Queue: Min Qin <qinmin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#875230}
GitOrigin-RevId: 156bc9fb70eb0e989279490a31a9bce83b54359f
1 file changed