toddlers: do not deploy toddlers in staging for now
    
    It is not ready to be deployed there from a configuration perspective
    and it may not make sense to run it there, at least for now
    (for example, we don't need to clean retired packages in stg, or check
    the email overrides file there).
    
    Signed-off-by: Pierre-Yves Chibon <pingou@pingoured.fr>