scsi: libsas: docs: Remove notify_ha_event()

The ->notify_ha_event() hook has long been removed from the libsas event
interface.

Remove it from documentation.

Link: https://lore.kernel.org/r/20210118100955.1761652-2-a.darwish@linutronix.de


Fixes: 042ebd29 ("scsi: libsas: kill useless ha_event and do some cleanup")
Cc: stable@vger.kernel.org
Reviewed-by: John Garry <john.garry@huawei.com>
Reviewed-by: Jack Wang <jinpu.wang@cloud.ionos.com>
Signed-off-by: Ahmed S. Darwish <a.darwish@linutronix.de>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>