The startup warning 'No user allowlists configured' only checked
GATEWAY_ALLOW_ALL_USERS and per-platform _ALLOWED_USERS vars. It
missed SIGNAL_GROUP_ALLOWED_USERS and per-platform _ALLOW_ALL_USERS
vars (e.g. TELEGRAM_ALLOW_ALL_USERS), causing a false warning even
when users had these configured. The actual auth check in
_is_user_authorized already recognized these vars.
Cherry-picked from PR #3202 by binhnt92.
Co-authored-by: binhnt92 <binhnt.ht.92@gmail.com>
