Issue #3343855 Removed constant not needed anymore

src/Session/SessionStorage.php

@@ -20,11 +20,6 @@ use Symfony\Component\Serializer\Serializer;
  */
 class SessionStorage implements SessionStorageInterface {
 
-  /**
-   * The serialization format to use for storing the session.
-   */
-  protected const SERIALIZATION_FORMAT = 'json';
-
   /**
    * The key value store to use.
    */