[Security] Bump phpmailer/phpmailer from 6.3.0 to 6.5.0

Bumps [phpmailer/phpmailer](https://github.com/PHPMailer/PHPMailer) from 6.3.0 to 6.5.0. **This update includes security fixes.**
- [Release notes](https://github.com/PHPMailer/PHPMailer/releases)
- [Changelog](https://github.com/PHPMailer/PHPMailer/blob/master/changelog.md)
- [Commits](PHPMailer/PHPMailer@v6.3.0...v6.5.0)

Signed-off-by: dependabot-preview[bot] <[email protected]>