Retrieve the email field rather than the bugzilla_email one
    
    The bugzilla_email relies on a user id -> email mapping that is kept
    in python-fedora fedora/client/fas2.py.
    That mapping is out-dated and, in fact, conflicts with the one used
    in this project in email_overrides.toml.
    
    So instead of retrieving the bugzilla_email, we retrieve the regular
    email and use our, up to date and maintained mapping to do the
    overrides.
    
    Otherwise, we end up in the situation described at:
    https://pagure.io/fesco/issue/2460#comment-669474
    where user A was marked as having an invalid account because they had
    a bugzilla_email entry that was returning an invalid bugzilla account.
    Changing to use the email field led to more people having invalid
    accounts because their mapping had not been updated.
    So let's make sure that mapping remains up to date now and use only
    one.
    
    Signed-off-by: Pierre-Yves Chibon <pingou@pingoured.fr>