[toddlers] Disable packager bugzilla sync on staging
    
    distgit_packager_bugzilla_sync toddler doesn't work well on staging, because the
    accounts from staging dist_git are not properly synced to staging bugzilla.
    which is causing this toddler to run for too long and blocking the queue.
    
    Signed-off-by: Michal Konečný <mkonecny@redhat.com>