osd/scrub: 'repairing' scrubs allowed at all times

Fix ScrubJob::observes_allowed_hours() to not block 'repairing'
scrubs outside of the allowed hours. This allows repair scrubs
to run at any time or day-of-week.
The fixed behaviour matches the documented requirements.

Fixes: https://tracker.ceph.com/issues/76811
Signed-off-by: Ronen Friedman <rfriedma@redhat.com>