Clear the federation blacklist

There's been plenty of discussion on defederation.

1. https://sh.itjust.works/post/103490
2. https://sh.itjust.works/post/216888
3. https://sh.itjust.works/post/229169
4. https://sh.itjust.works/post/151703

I propose we defederate no instance other than those with egregiously illegal content such as CP. Note that I know of no such instances.

As of the moment of this post, the only defederated instance is lemmygrad.ml, so voting Yea would refederate them. It's a genocide-denying Marxist instance.