ZTS: Retire "ci_reason" exceptions

There is no longer be a need for the ci_reason exception with
the update CI GitHub Actions infrastruture. Retire it.

Reviewed-by: Tino Reichardt <milky-zfs@mcmilk.de>
Reviewed-by: George Melikov <mail@gmelikov.ru>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #16553