Remove duplication in comments votes component

We're also simplifying the code a bit by removing the
`participation-allowed` HTML class, which wasn't used in any other votes
component.

app/assets/javascripts/votes.js

@@ -5,11 +5,9 @@
       $(document).on({
         "mouseenter focus": function() {
           $("div.participation-not-allowed", this).show();
-          $("div.participation-allowed", this).hide();
         },
         mouseleave: function() {
           $("div.participation-not-allowed", this).hide();
-          $("div.participation-allowed", this).show();
         }
       }, votes);
     },