releng-bot: drop alias in favor of fixing address in fas
    
    Right now releng-bot has a fas address of 'releng-bot@fedoraproject.org'
    which is... confusing. The alias overrides this and sends email to
    admin, but it results in a duplicate, causing the cron job to send mail
    about the duplicate everytime newaliases run.
    
    So, instead drop the alias here and switch the user in fas to be
    admin+relengbot. This will still go to admin, not run into problems with
    the address already in use in fas and should cause the newaliases to
    stop complaining.
    
    Signed-off-by: Kevin Fenzi <kevin@scrye.com>