How do I make certain vanilla mobs not spawn in certain vanilla biomes?

So, I'm trying to have the skeleton mob not spawn in the desert since I added a variant of it for the desert (kinda like the husk and stray which spawn in place of the zombie and skeleton respectively.) What do I do to achieve this? I know you need mixins, which I have (I have NerdyPuzzle's mixins plugin) but I don't really know much about coding so if any of you know how I could do this, that would be greatly appreciated.