[doc] use separate playbooks for upgrade
    
    There is a problem with our current playbooks, that they can be
    executed automatically without us knowing about it. That is an issue
    particularly during release process because we can prepare new
    packages into infra-tags repo or bodhi and a nightly reprovision
    can upgrade to them outside of an outage window or any of us being
    prepared for it.
    
    Therefore `groups/copr-*.yml` playbooks *should not* upgrade any
    packages, but only ensure, that those packages are installed. For
    upgrade, there should be separate `manual/copr/copr-*-upgrade.yml`
    playbooks. Because they are located under `manual` directory, it
    is secured, that they can't be run automatically.