Update jug_of_selbina_milk.lua

previous version would not allow regen effect application due to caster:getEquipID(SLOT_BODY); returning a nil value. Once changed to target:getEquipID, function would continue on past body check, never registering item was being worn, and returning standard regen value.
local variable has been removed entirely, and body slot is now compared directly to target:getEquipID(SLOT_BODY); to check if dream robe+1 is being worn.