search: remove legacy 'search[sort]' params.

Remove support for the `search[sort]` param on certain index pages. This
hasn't been used for years, and it caused the `search[order]=` param to
be added to pagination links even when the order was blank.

app/models/artist.rb

@@ -502,7 +502,6 @@ class Artist < ApplicationRecord
         q = q.includes(:tag).where("tags.name IS NULL OR tags.post_count <= 0").references(:tags)
       end
 
-      params[:order] ||= params.delete(:sort)
       case params[:order]
       when "name"
         q = q.order("artists.name")

app/models/artist_version.rb

@@ -11,7 +11,6 @@ class ArtistVersion < ApplicationRecord
 
       q = q.search_attributes(params, :updater, :is_active, :is_banned, :artist_id, :name, :group_name)
 
-      params[:order] ||= params.delete(:sort)
       if params[:order] == "name"
         q = q.order("artist_versions.name").default_order
       else

app/models/pool.rb

@@ -70,7 +70,6 @@ class Pool < ApplicationRecord
         q = q.collection
       end
 
-      params[:order] ||= params.delete(:sort)
       case params[:order]
       when "name"
         q = q.order("pools.name")

app/models/tag.rb

@@ -853,7 +853,6 @@ class Tag < ApplicationRecord
         q = q.joins("LEFT JOIN artists ON tags.name = artists.name").where("artists.name IS NULL OR artists.is_active = false")
       end
 
-      params[:order] ||= params.delete(:sort)
       case params[:order]
       when "name"
         q = q.order("name")

app/models/wiki_page.rb

@@ -101,7 +101,6 @@ class WikiPage < ApplicationRecord
         q = q.where("other_names is null or other_names = '{}'")
       end
 
-      params[:order] ||= params.delete(:sort)
       case params[:order]
       when "title"
         q = q.order("title")