Remove poison immunity from snow giants

Because why is it there?  Undead and various other unliving things give enough poison woes as is, no need to put it on random humanoids.

game/modules/tome/data/general/npcs/snow-giant.lua

@@ -45,7 +45,6 @@ newEntity{
 
 	no_breath = 1,
 	confusion_immune = 1,
-	poison_immune = 1,
 	ingredient_on_death = "SNOW_GIANT_KIDNEY",
 }