discussions: add a short voting hint to tickets
    
    Multiple people mentioned they often forget how to vote and need to study the
    documentation repeatedly. It seems that a very short hint on the most basic
    voting command would make their experience better.
    
    Fixes https://pagure.io/fedora-qa/blockerbugs/issue/152
    Fixes https://pagure.io/fedora-qa/blockerbugs/pull-request/157