approvals: remove post undelete endpoint.

Remove `POST /moderator/post/undelete` endpoint. Replace it with
`POST /post_approvals` instead.

Fixes it so that undeleting a post has the same behavior as approving a
post. Namely, it reloads the page instead of just flashing a "Post was
undeleted" message.

app/controllers/moderator/post/posts_controller.rb

@@ -1,7 +1,7 @@
 module Moderator
   module Post
     class PostsController < ApplicationController
-      before_action :approver_only, :only => [:delete, :undelete, :move_favorites, :ban, :unban, :confirm_delete, :confirm_move_favorites, :confirm_ban]
+      before_action :approver_only, :only => [:delete, :move_favorites, :ban, :unban, :confirm_delete, :confirm_move_favorites, :confirm_ban]
       before_action :admin_only, :only => [:expunge]
       skip_before_action :api_check
 
@@ -19,11 +19,6 @@ module Moderator
         redirect_to(post_path(@post))
       end
 
-      def undelete
-        @post = ::Post.find(params[:id])
-        @post.approve!
-      end
-
       def confirm_move_favorites
         @post = ::Post.find(params[:id])
       end

app/views/moderator/post/posts/undelete.js.erb

@@ -1,3 +0,0 @@
-$("#c-posts #delete").show();
-$("#c-posts #undelete").hide();
-Danbooru.notice("Post was undeleted");

app/views/posts/partials/show/_options.html.erb

@@ -42,7 +42,7 @@
 
       <% if CurrentUser.can_approve_posts? %>
         <% if post.is_deleted? %>
-          <li id="post-option-undelete"><%= link_to "Undelete", undelete_moderator_post_post_path(post_id: post.id), remote: true, method: :post, "data-confirm": "Are you sure you want to undelete this post?" %></li>
+          <li id="post-option-undelete"><%= link_to "Undelete", post_approvals_path(post_id: post.id), remote: true, method: :post, "data-confirm": "Are you sure you want to undelete this post?" %></li>
           <% if post.fav_count > 0 && post.parent_id %>
             <li id="post-option-move-favorites"><%= link_to "Move favorites", confirm_move_favorites_moderator_post_post_path(post_id: post.id) %></li>
           <% end %>