No more zombies in xenobio (#21503)

* Update mystery_box.dm

* Update mystery_box.dm

Author: Moltijoe

code/game/objects/effects/spawners/mystery_box.dm

@@ -152,6 +152,7 @@
 	var/static/list/spooks = list('sound/hallucinations/growl1.ogg','sound/hallucinations/growl2.ogg','sound/hallucinations/growl3.ogg','sound/hallucinations/veryfar_noise.ogg','sound/hallucinations/wail.ogg')
 	armor = 20
 	speedmod = 1.6
+	changesource_flags = MIRROR_BADMIN //deliberate admin spawn only
 	var/heal_rate = 1
 	var/regen_cooldown = 0