datastore_backup - Move backups to a weekly cadence.
datastore_backup - Move backups to a weekly cadence.

Change-Id: Ia431281bc12c9fb20120a2f342bb3b358042e427
Reviewed-on: https://skia-review.googlesource.com/c/buildbot/+/245584
Commit-Queue: Joe Gregorio <b9cf2471ff6d33504cafe8e6f356b732b2cadced@google.com>
Reviewed-by: Ravi Mistry <9fa2e7438b8cb730f96b74865492597170561628@google.com>

google/skia-buildbot,google/skia-buildbot,google/skia-buildbot,google/skia-buildbot,google/skia-buildbot,google/skia-buildbot,google/skia-buildbot,google/skia-buildbot