(Java Parity) Remove non-chicken zombie jockeys

Java Edition added chicken jockeys -- a baby zombie riding a chicken. This was a creative idea and led to an iconic, unique, interesting mob.

Back when this feature was ported to Bedrock Edition, the devs did not consider parity a priority and added lots of other potential mounts -- ocelots, wolves, cows, pigs, sheep, spiders, even other zombies. This diluted the appeal of chicken jockeys by watering down the concept to "baby zombies can ride other mobs," which is far less interesting.

Now that parity is a priority, these combinations should be removed from Bedrock Edition, leaving only the classic chicken jockey.