ceph.spec.in: add man/rgw-gap-list

Introduced in ceph#62749
Centos builds fail with:
```
error: Installed (but unpackaged) file(s) found:
   /usr/share/man/man8/rgw-gap-list.8.gz

RPM build errors:
    Installed (but unpackaged) file(s) found:
   /usr/share/man/man8/rgw-gap-list.8.gz
```

Signed-off-by: Matan Breizman <[email protected]>

Author: Matan-B

ceph.spec.in

@@ -1836,6 +1836,7 @@ exit 0
 %{_mandir}/man8/rbd-replay-many.8*
 %{_mandir}/man8/rbd-replay-prep.8*
 %{_mandir}/man8/rgw-orphan-list.8*
+%{_mandir}/man8/rgw-gap-list.8*
 %{_mandir}/man8/rgw-restore-bucket-index.8*
 %dir %{_datadir}/ceph/
 %{_datadir}/ceph/known_hosts_drop.ceph.com