debian,ceph.spec: fix ceph-osd upgrade conflicts

debian,ceph.spec: fix ceph-osd upgrade conflicts

With https://github.com/ceph/ceph/pull/65782 merged, upgrading ceph-osd
would need to replace the previous ceph-osd existing on the machine.
Otherwise, we won't be able to symlink the newly installed package:
```
2025-12-05T21:09:20.472 INFO:teuthology.orchestra.run.smithi077.stdout:
Installing       : ceph-osd-classic-2:20.3.0-4434.g8611241d.el9.x86_6
24/87
2025-12-05T21:09:20.478 INFO:teuthology.orchestra.run.smithi077.stdout:
Running scriptlet: ceph-osd-classic-2:20.3.0-4434.g8611241d.el9.x86_6
24/87
2025-12-05T21:09:20.479
INFO:teuthology.orchestra.run.smithi077.stdout:failed to link
/usr/bin/ceph-osd -> /etc/alternatives/ceph-osd: /usr/bin/ceph-osd
exists and it is not a symlink
```

Signed-off-by: Matan Breizman <mbreizma@redhat.com>