Add a link to reject a broadcast

If a broadcast definitely shouldn’t go out (for example because it has a
spelling mistake or is going to the wrong areas) then we should have a
way of removing it. Once it’s removed no-one else can approve it, and it
isn’t cluttering up the dashboard.

This is a link (because it’s a secondary action) and red (because it’s
destructive, in that it’s throwing away someone’s work).

app/assets/stylesheets/components/page-footer.scss

@@ -7,6 +7,7 @@
 
     line-height: 40px;
     padding: 1px 0 0 15px;
+    font-weight: normal;
 
   }