Downgrade activitypub-federation library to 0.4.1 by Nutomic · Pull Request #3466 · LemmyNet/lemmy - Lemmy 0.18.1 change regarding overloaded servers

" I believe that it is responsible for major increases in CPU and RAM usage and client errors. Because now there are up to millions of async tasks active which are doing nothing but sleeping, and this likely messes up the scheduler. I will rework this for 0.18.2."