Don't need these keys with the new format either.

extras/repair.chain.yml

@@ -47,26 +47,14 @@ Repairables:
     ###
     # Armor
     CHAINMAIL_HELMET:
-        ItemType: ARMOR
         RepairMaterial: FIRE
-        MaximumDurability: 165
-        MinimumQuantity: 5
         XpMultiplier: 2
     CHAINMAIL_CHESTPLATE:
-        ItemType: ARMOR
         RepairMaterial: FIRE
-        MaximumDurability: 240
-        MinimumQuantity: 8
         XpMultiplier: 2
     CHAINMAIL_LEGGINGS:
-        ItemType: ARMOR
         RepairMaterial: FIRE
-        MaximumDurability: 225
-        MinimumQuantity: 7
         XpMultiplier: 2
     CHAINMAIL_BOOTS:
-        ItemType: ARMOR
         RepairMaterial: FIRE
-        MaximumDurability: 195
-        MinimumQuantity: 4
         XpMultiplier: 2