voting policy: clarify/change voting policy for Non-resp. maintainers
    
    In the description of the general voting rules, mention that NRM ticket have
    their own policy and the usual voting policy does not apply to them.
    
    In the description of the NRM voting, mention that the policy is different.
    
    Also change the text to say that the ticket will be added to meeting agenda only
    if there's a disagreement. Previous text implied that the ticket would be
    handled in a meeting if no votes were made. The new text matches the actual
    practice that was being followed.
    
    Fixes https://pagure.io/fesco/issue/3166.