Edit "Monsters Hunted" to target hostile Jockeys rather than neutral Mounts

As it stands, Zombie Horses, Camel Husks, and Zombie Nautiluses are all required to achieve the "Monsters Hunted" advancement. However, because they can be tamed and ridden by the player after the rider is unseated, this seems like something of a waste (as well as just kind of feeling bad). It should be entirely possible to substitute in the riding mobs rather than the ridden ones, considering that the Lava Chicken music disc drops from the Zombie in the Chicken Jockey pairing. Counting the mob riding the mount toward the advancement accomplishes the same thing without forcing the player to put down what could otherwise be a cool ride and/or companion. That, or make it an either/or thing, so that players who kill the mount first, inadvertently or otherwise, aren't disadvantaged for having done so.