Issue #3297233: Update documentation for removal of file_create_url()

Function was removed in 32328453.

src/Plugin/FillPdfActionPlugin/FillPdfRedirectAction.php

@@ -25,9 +25,6 @@ class FillPdfRedirectAction extends FillPdfSaveAction {
    * @return \Symfony\Component\HttpFoundation\RedirectResponse
    *   Redirects user to the generated PDF file, or if saving the file fails,
    *   to the front page.
-   *
-   * @todo Replace file_create_url() by File::createFileUrl() once we're not
-   *   supporting Drupal 8.6 anymore.
    */
   public function execute() {
     $saved_file = $this->savePdf();