no prejoin page with JWT

fairmeeting domains with a JWT usually do not need a prejoin page, as the users know how to use fairmeeting.

Else with a JWT they get back to a join page after they joined, so we set

       prejoinPageEnabled: false,

• pro
• ekir
• ekbo
• rp
• agme

also prejoin stops from re-connecting automatically to room, so submitted issue https://github.com/jitsi/jitsi-meet/issues/13948