We're migrating to using the cleaner zulip.com domain, which involves
changing all of our links from ReadTheDocs and other places to point
to the cleaner URL.
OneLogin has removed the app that these instructions used to rely on.
This app choice should be more stable, as there are other providers
that rely on it in their instructions for setting them up with OneLogin.
Ideally, in the future, we'll get our own app added to OneLogin's app
catalogue, which will simplify the setup process for administrators.