Fixes call to undefined method 'queueNewOrderEmail' on PayPal webhook callback

[peterschen]

When the webhook call is triggered by PayPal it fails with a 503 and exception.log will show something like this (for whatever reason the errors are German on my system):

2022-01-24 16:18:46] main.CRITICAL: Ungültige Methode Magento\Sales\Model\Order\Interceptor:: queueNewOrderEmail {"exception":"[object] (Magento\\Framework\\Exception\\LocalizedException(code: 0): Ungültige Methode Magento\\Sales\\Model\\Order\\Interceptor:: queueNewOrderEmail at /var/www/[REDACTED]/magento2/vendor/magento/framework/DataObject.php:399)"} []

Model\Webhook\Event.php uses the method queueNewOrderEmail which is no available anymore and emails should be sent using Magento\Sales\Model\Order\Email\Sender\InvoiceSender. This PR will remove usage of queueNewOrderEmail and use InvoiceSender instead to send the email.