posts: remove ban confirmation page.

Use a dialog instead of a separate page to confirm bans.

app/views/moderator/post/posts/confirm_ban.html.erb

@@ -1,12 +0,0 @@
-<h1>Ban Post</h1>
-
-<div>
-  <%= PostPresenter.preview(@post, show_deleted: true) %>
-</div>
-
-<%= form_tag(ban_moderator_post_post_path(@post), :style => "clear: both;", :class => "simple_form") do %>
-  <p>Banning a post will hide it from anyone without a gold level account or higher. You should only ban a post if an artist requested it.</p>
-
-  <%= submit_tag "Ban" %>
-  <%= submit_tag "Cancel" %>
-<% end %>