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Updates the expires_after attribute for 21 histograms that have
been used to generate alerts in the past 90 days and do not already have
a date later than or within 60 days of 2021-04-05.

TBR=chromium-metrics-reviews@google.com

Change-Id: I11e1f8ba0d308fd6a68b83bb323142beefb33734
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2611345Reviewed-by: Chrome Metrics Logs <chrome-metrics-team+robot@google.com>
Commit-Queue: Chrome Metrics Logs <chrome-metrics-team+robot@google.com>
Cr-Commit-Position: refs/heads/master@{#840241}