-$email = $this->swift->createMessage('message');
+$email = new \Symfony\Component\Mime\Email();

Configure your rector.php:

<?php

use Rector\Config\RectorConfig;
use Rector\Symfony\SwiftMailer\Rector\MethodCall\SwiftCreateMessageToNewEmailRector;

return RectorConfig::configure()
 ->withRules([
 SwiftCreateMessageToNewEmailRector::class,
 ]);