Remove Mo' Creatures support

[Plastikmensch]

The Mo' Creatures mod has been discontinued since Minecraft 1.12.
While some forks exist which try to keep it updated, it doesn't make sense to support them.
This plugin is also primarily developed for Paper. It might work with forge, it might not.
I cannot make any guarantee of functionality and I cannot and do not test it.
Just judging by looking at the code, it shouldn't work anyway, it just needlessly complicates the code.
If such a feature is wanted in the future and there is a consistent fork, it could be added back again.