Describe the bug
In section 6, the documentation still instructs users to use experimental_features.msc3861, which, according to Synapse docs, is deprecated and will be removed in v1.137.0.

To Reproduce
Open documentation in section 6 - https://element-hq.github.io/matrix-authentication-service/setup/homeserver.html

Expected behavior
Documentation on how to setup homeserver should be up to date