Reduce log clutter from backup system

[iffy]

This is too much, especially if you have multiple budgets:

[2023-06-21 19:21:29.652] [info] (core) INFO (backups) Backing up My Budget.buckets ...
[2023-06-21 19:21:29.683] [info] (core) INFO (backups)   KEEP 2023-04-25-111322_auto.buckets.gz
[2023-06-21 19:21:29.685] [info] (core) INFO (backups)   KEEP 2023-06-09-224239_auto.buckets.gz
[2023-06-21 19:21:29.685] [info] (core) INFO (backups)   KEEP 2023-06-16-213434_auto.buckets.gz
[2023-06-21 19:21:29.685] [info] (core) INFO (backups)   KEEP 2023-06-18-222843_auto.buckets.gz
[2023-06-21 19:21:29.685] [info] (core) INFO (backups)   DEL  2023-06-21-180428_auto.buckets.gz
[2023-06-21 19:21:29.685] [info] (core) INFO (backups)   KEEP 2023-06-21-181528_auto.buckets.gz
[2023-06-21 19:21:29.685] [info] (core) INFO (backups)   KEEP 2023-06-21-182628_auto.buckets.gz
[2023-06-21 19:21:29.685] [info] (core) INFO (backups)   KEEP 2023-06-21-183728_auto.buckets.gz
[2023-06-21 19:21:29.686] [info] (core) INFO (backups)   KEEP 2023-06-21-184829_auto.buckets.gz
[2023-06-21 19:21:29.686] [info] (core) INFO (backups)   KEEP 2023-06-21-185929_auto.buckets.gz
[2023-06-21 19:21:29.686] [info] (core) INFO (backups)   KEEP 2023-06-21-191029_auto.buckets.gz
[2023-06-21 19:21:29.713] [info] (core) INFO (backups)   NEW  2023-06-21-192129_auto.buckets.gz

[iffy]

Included in v0.71.0 release (AUTOMATED COMMENT)