Drop from distgit_bugzilla_sync the feature to email users
    
    Back when we had only this script to do everything, we needed a way
    to warn users that their accounts was not properly set-up. We also
    did not want to keep sending that information, so we built a cache
    file on disk that we'd use as a way to ensure we only notify people
    once per day or so.
    Now we have a toddler called: packagers_without_bugzilla that runs
    once a day and does just that: inform packagers who do not have a
    valid bugzilla account about the need to fix this situation.
    Since that toddler does that, there is no need for distgit_bugzilla_sync
    to have to support it. It can keep on running at the frequency it
    wants and just inform admins when it ran into some errors.
    
    Signed-off-by: Pierre-Yves Chibon <pingou@pingoured.fr>