models: remove nonexistent associations.

Remove the WikiPageVersion#artist and Post#updater associations. Neither
of these existed and they caused problems with searching includable
associations in the API.

app/models/post.rb

@@ -39,7 +39,6 @@ class Post < ApplicationRecord
   after_commit :remove_iqdb_async, :on => :destroy
   after_commit :update_iqdb_async, :on => :create
 
-  belongs_to :updater, :class_name => "User", optional: true # this is handled in versions
   belongs_to :approver, class_name: "User", optional: true
   belongs_to :uploader, :class_name => "User", :counter_cache => "post_upload_count"
   belongs_to :parent, class_name: "Post", optional: true
@@ -1295,7 +1294,7 @@ class Post < ApplicationRecord
         :is_note_locked, :is_rating_locked, :is_status_locked, :is_pending,
         :is_flagged, :is_deleted, :is_banned, :last_comment_bumped_at,
         :last_commented_at, :last_noted_at, :uploader_ip_addr,
-        :uploader, :updater, :approver, :parent, :upload, :artist_commentary,
+        :uploader, :approver, :parent, :upload, :artist_commentary,
         :flags, :appeals, :notes, :comments, :children, :approvals,
         :replacements, :pixiv_ugoira_frame_data
       )

app/models/wiki_page_version.rb

@@ -2,12 +2,11 @@ class WikiPageVersion < ApplicationRecord
   array_attribute :other_names
   belongs_to :wiki_page
   belongs_to_updater
-  belongs_to :artist, optional: true
   belongs_to :tag, primary_key: :name, foreign_key: :title, optional: true
 
   module SearchMethods
     def search(params)
-      q = search_attributes(params, :id, :created_at, :updated_at, :title, :body, :other_names, :is_locked, :is_deleted, :updater, :wiki_page, :artist, :tag)
+      q = search_attributes(params, :id, :created_at, :updated_at, :title, :body, :other_names, :is_locked, :is_deleted, :updater, :wiki_page, :tag)
       q = q.text_attribute_matches(:title, params[:title_matches])
       q = q.text_attribute_matches(:body, params[:body_matches])
 
@@ -76,6 +75,6 @@ class WikiPageVersion < ApplicationRecord
   end
 
   def self.available_includes
-    [:updater, :wiki_page, :artist, :tag]
+    [:updater, :wiki_page, :tag]
   end
 end