The arms of zombies and their variants are incorrectly positioned when holding spears in the off hand

Since the fix for MC-304213, Zombie-type mob now enter a player-like animation (with both arms hanging straight down) when holding a spear in their offhand.

Steps to Reproduce:

1. Summon a zombie with a spear in the offhand.

2. Observe the zombie's arm animation.

3. Notice that the zombie's arms are hanging straight down, identical to the player's state, rather than being stretched forward like a normal zombie.