GDM: Authentication mode selection is briefly shown before automatic selection

When logging in via GDM with a user that already exists and has a local password set, GDM very briefly shows the "Select the authentication mode" UI elements, before it automatically selects local password authentication. It also happens on the lock screen.

That's a longstanding issue, I see it both with authd 0.4.2 and 0.5.3, but I couldn't find an existing GitHub issue for this.