*Scan: Prolong expiration milestone for histograms

Bug: 11297512
Change-Id: I488572ceb283a48f726474f3afe321f8a2a2caf3
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3081824


Auto-Submit: Anton Bikineev <bikineev@chromium.org>
Reviewed-by: Steven Holte <holte@chromium.org>
Commit-Queue: Anton Bikineev <bikineev@chromium.org>
Cr-Commit-Position: refs/heads/master@{#911213}