user.rb: drop unused add_favorite!, delete_favorite! methods.

These methods were incorrect anyway, didn't upvote/downvote the post.

app/models/user.rb

@@ -108,6 +108,7 @@ class User < ApplicationRecord
   has_many :forum_posts, -> {order("forum_posts.created_at, forum_posts.id")}, :foreign_key => "creator_id"
   has_many :user_name_change_requests, -> {visible.order("user_name_change_requests.created_at desc")}
   has_many :favorite_groups, -> {order(name: :asc)}, foreign_key: :creator_id
+  has_many :favorites, ->(rec) {where("user_id % 100 = #{rec.id % 100} and user_id = #{rec.id}").order("id desc")}
   belongs_to :inviter, class_name: "User", optional: true
   after_update :create_mod_action
   accepts_nested_attributes_for :dmail_filter
@@ -297,20 +298,6 @@ class User < ApplicationRecord
     end
   end
 
-  module FavoriteMethods
-    def favorites
-      Favorite.where("user_id % 100 = #{id % 100} and user_id = #{id}").order("id desc")
-    end
-
-    def add_favorite!(post)
-      Favorite.add(post: post, user: self)
-    end
-
-    def remove_favorite!(post)
-      Favorite.remove(post: post, user: self)
-    end
-  end
-
   module LevelMethods
     extend ActiveSupport::Concern
 
@@ -917,7 +904,6 @@ class User < ApplicationRecord
   include NameMethods
   include PasswordMethods
   include AuthenticationMethods
-  include FavoriteMethods
   include LevelMethods
   include EmailMethods
   include BlacklistMethods