Issue #3314143: Add documentation for testing minor updates

src/Form/UpdaterForm.php

@@ -301,6 +301,8 @@ final class UpdaterForm extends FormBase {
           ->setRouteParameter('name', 'automatic_updates')
           ->setOption('fragment', 'minor-update');
 
+        // @todo Updating this wording in https://www.drupal.org/i/3280403 to
+        //   reflect that multiple minor branches may be visible.
         $form['minor_update_help'] = [
           '#markup' => $this->t('The following updates are in the next minor version of Drupal. <a href=":url">Learn more about updating to another minor version.</a>', [
             ':url' => $url->toString(),