Correctly undo concurrent rename

Use the method that will remove the right trigger. Previously, it seems
we did not remove the trigger from the up method at all.

db/migrate/20190801193427_rename_application_settings_snowplow_collector_uri_column.rb

@@ -12,6 +12,6 @@ class RenameApplicationSettingsSnowplowCollectorUriColumn < ActiveRecord::Migrat
   end
 
   def down
-    cleanup_concurrent_column_rename :application_settings, :snowplow_collector_hostname, :snowplow_collector_uri
+    undo_rename_column_concurrently :application_settings, :snowplow_collector_uri, :snowplow_collector_hostname
   end
 end