This PR makes the sender name nullable to avoid deprecation errors

[johnkhansrc]

Deprecated: Brevo\Client\Model\SendSmtpEmailSender::__construct(): Implicitly marking parameter $data as nullable is deprecated, the explicit nullable type must be used instead in /app/vendor/getbrevo/brevo-php/lib/Model/SendSmtpEmailSender.php on line 189

[sonarqubecloud[bot]]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[nclavaud]

This change is already included in https://github.com/getbrevo/brevo-php/pull/51