Resolve #3631374 "Fix php 8.4"

On PHP 8.4, loading Maestro’s workflow editor produces the following deprecation warning:

MaestroWebformTask::__construct(): Implicitly marking parameter $configuration as nullable is deprecated, the explicit nullable type must be used instead. The constructor in modules/maestro_webform/src/Plugin/EngineTasks/MaestroWebformTask.php declares an array parameter with a default value of NULL:

public function __construct(array $configuration = NULL)