Revert old Ice plains biome mobs

Please reverse the old changes where previous hostile mobs and passive mobs spawn in the ice plains / snowy tundra.

It's boring seeing only strays (bedrock) and only rabbits and polar bears. I wish there were the original hostile mobs like in Java and the old passive mobs such as sheep and cows etc. However of course they would have small spawn rates, but it is better than none.