artists: reduce queries in artist summaries.

Avoid a few queries when searching for single artist tags.

app/models/artist.rb

@@ -386,14 +386,6 @@ class Artist < ApplicationRecord
   end
 
   module TagMethods
-    def has_tag_alias?
-      TagAlias.active.exists?(["antecedent_name = ?", name])
-    end
-
-    def tag_alias_name
-      TagAlias.active.find_by_antecedent_name(name).consequent_name
-    end
-
     def category_name
       Tag.category_for(name)
     end