[MC-220803] Librarians never offer treasure enchantments for an odd number of emeralds

The bug

I ran through breaking and placing a lectern several hundred times, and Mending, Frost Walker I and II, and Curse books always costed an even number of emeralds. There should not be an odd-even bias, as it doesn't make logical sense and no other enchantments have this.

Steps to reproduce:

Spawn villager
Place lectern
Check enchanted book trade
Break lectern
Repeat several hundred times

The cost of a treasure enchantment is never an odd number of emeralds.