Fix #4359: Allow builders to move small (artist) tags manually.

Allow builders to approve artist alias BURs. The BUR must contain only
artist aliases or mass updates and each artist must have less than 100
posts.

app/models/bulk_update_request.rb

@@ -136,6 +136,10 @@ class BulkUpdateRequest < ApplicationRecord
     @processor ||= BulkUpdateRequestProcessor.new(script, forum_topic_id: forum_topic_id, skip_secondary_validations: skip_secondary_validations)
   end
 
+  def is_tag_move_allowed?
+    processor.is_tag_move_allowed?
+  end
+
   def is_pending?
     status == "pending"
   end