Remove final from Barcode FieldFormatterPlugin

Closes #3405065

src/Plugin/Block/Barcode.php

@@ -21,7 +21,7 @@ use Symfony\Component\DependencyInjection\ContainerInterface;
  *  admin_label = @Translation("Barcode"),
  * )
  */
-final class Barcode extends BlockBase implements ContainerFactoryPluginInterface {
+class Barcode extends BlockBase implements ContainerFactoryPluginInterface {
 
   /**
    * A logger instance.