ddns: removed too restrictive assert.

 - this could happen when reloading

src/knot/nameserver/update.c

@@ -134,7 +134,6 @@ static int sign_update(zone_t *zone, const zone_contents_t *old_contents,
 
 	// Plan next zone resign.
 	const time_t resign_time = zone_events_get_time(zone, ZONE_EVENT_DNSSEC);
-	assert(resign_time > ZONE_EVENT_NOW);
 	if (time(NULL) + refresh_at < resign_time) {
 		zone_events_schedule(zone, ZONE_EVENT_DNSSEC, refresh_at);
 	}