Follow up to d5ef91af which adds a missing 'obsoletes' for the
libzfs-devel package.
Add a comment to the zfs.spec file as a reminder that previous
versions of the package should be marked as obsolete.
Reviewed-by: Olaf Faaland <faaland1@llnl.gov>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes#11844Closes#11895
3e660534ea