Remove unnecessary class from comment edit form

This was causing a left border to show up, and doesn't seem to be
getting used for anything.

tildes/tildes/templates/intercooler/comment_edit.jinja2

@@ -4,7 +4,6 @@
 {% from 'macros/forms.jinja2' import markdown_textarea %}
 
 <form method="post"
-    class="comment"
     autocomplete="off"
     data-ic-patch-to="{{ request.route_url(
       'ic_comment',