Zombies spawning on Zombie Horse cannot spawn with Copper Armor

Steps to Reproduce:

1. Find zombie horses with riders in world

Expected Result:

Around a third of the armoured ones should have copper armour.

Actual Result:

None of them have copper armour.

Zombies spawning on zombie horse cannot spawn with copper armour because the zombie_rider_equipment loot table in the vanilla behaviour pack has the old armour loot table contained within it.

How to Fix:

Update the zombie_rider_equipment loot table to have the new zombie_gear armour loot table contained within it instead of the pre copper update one (and update the armour tier calculation as this was a bug in the copper update before as well).