admin db: reduce the backup history

to save space on the backup server

Test Plan

diff origin/production/backup01.euwest.azure.internal.softwareheritage.org current/backup01.euwest.azure.internal.softwareheritage.org
*******************************************
  File[/etc/sanoid/sanoid.conf] =>
   parameters =>
     content =>
      @@ -5,11 +5,11 @@
         use_template = backup
         hourly = 0
      -  monthly = 2
      -  daily = 30
      +  monthly = 1
      +  daily = 15
       [data/sync/dali/postgresql/wal]
         use_template = backup
         hourly = 0
      -  monthly = 2
      -  daily = 30
      +  monthly = 1
      +  daily = 15
      _
      _
*******************************************
*** End octocatalog-diff on backup01.euwest.azure.internal.softwareheritage.org

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Migrated from D7341 (view on Phabricator)