Mobs: Don't set gotten in API anymore

mods/ENTITIES/mcl_mobs/api.lua

@@ -1142,11 +1142,6 @@ local replace = function(self, pos)
 				minetest.set_node(pos, {name = with})
 			end
 
-			-- when cow/sheep eats grass, replace wool and milk
-			if self.gotten == true then
-				self.gotten = false
-				self.object:set_properties(self)
-			end
 		end
 	end
 end
@@ -3780,8 +3775,6 @@ function mobs:feed_tame(self, clicker, feed_count, breed, tame)
 				self.horny = true
 			end
 
-			self.gotten = false
-
 			if tame then
 
 				self.tamed = true

mods/ENTITIES/mcl_mobs/api.txt

@@ -303,8 +303,10 @@ for each mob.
    'self.child_texture' contains mob child texture when growing up
    'self.base_texture'  contains current skin texture which was randomly
                         selected from textures list
-   'self.gotten'        this is used for obtaining milk from cow and wool from
-                        sheep
+   'self.gotten'        this is used to track whether some special item has been
+                        gotten from the mob, for example, wool from sheep.
+                        Initialized as false, and the mob must set this value
+                        manually.
    'self.horny'         when animal fed enough it is set to true and animal can
                         breed with same animal
    'self.hornytimer'    background timer that controls breeding functions and