make skeleton horses better when underwater

the main feature of skeleton horses over regular horses is that they can go underwater, but they are really slow, making them pretty useless. considering how rare they are, i think they should be at least similar to the speed regular horses are on land

additionally, since skeleton horses fall so slowly underwater when it jumps it can get stuck on a block, making it have to fall down to block below before climbing to the next block, which is just kind of inconvenient