Fortress Spawned Wither Skeletons have the wrong loot table in withered forests

[bananathrowingmachine]

While they move like regular wither skeletons, they do not drop skulls, if the wither skeletons are spawned within a withered forest, even if player spawned, command spawned, and/or fortress spawned

[catter1]

Fixed for 5.1.5.