Bug 30588: (QA follow-up) Clear waiting-for-2FA-setup in session

Bug 30588: (QA follow-up) Clear waiting-for-2FA-setup in session

If we do not clear this session, the first login directly after setup
does not really enhances user experience ;)

Test plan:
Make sure 2FA is enforced.
Test the above. Disable your 2FA, logout and login.
Verify that you can access pages with this patch now. Without this
patch you could not.
Run these tests to provide more confidence:
t/db_dependent/Auth.t
t/db_dependent/api/v1/two_factor_auth.t
t/db_dependent/Koha/Auth/TwoFactorAuth.t

Signed-off-by: Marcel de Rooy <m.de.rooy@rijksmuseum.nl>
Signed-off-by: Nick Clemens <nick@bywatersolutions.com>
Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>