Use a button to delete comments

As mentioned in commit 5311daadf, there are several reasons to use
buttons in these situations. And, as mentioned in the previous commits,
using buttons instead of links for actions requiring confirmation will
help us test for accessibility issues.

app/views/comments/_actions.html.erb

@@ -5,10 +5,10 @@
 <% if can?(:hide, comment) || can?(:hide, comment.user) %>
   <% if comment.author == current_user %>
     <span class="divider">&nbsp;&bull;&nbsp;</span>
-    <%= link_to t("comments.actions.delete"),
-                hide_comment_path(comment),
-                method: :put, remote: true, class: "delete-comment",
-                data: { confirm: t("comments.actions.confirm_delete") } %>
+    <%= button_to t("comments.actions.delete"),
+                  hide_comment_path(comment),
+                  method: :put, remote: true, class: "delete-comment", form_class: "delete-comment-form",
+                  data: { confirm: t("comments.actions.confirm_delete") } %>
   <% else %>
     <%= render Shared::ModerationActionsComponent.new(comment) %>
   <% end %>