build(deps): update phpmailer/phpmailer requirement from ^6.0 to ^7.0

Updates the requirements on [phpmailer/phpmailer](https://github.com/PHPMailer/PHPMailer) to permit the latest version.
- [Release notes](https://github.com/PHPMailer/PHPMailer/releases)
- [Changelog](https://github.com/PHPMailer/PHPMailer/blob/master/changelog.md)
- [Commits](PHPMailer/PHPMailer@v6.0.0...v7.0.0)

---
updated-dependencies:
- dependency-name: phpmailer/phpmailer
  dependency-version: 7.0.0
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

composer.json

@@ -54,7 +54,7 @@
         "monolog/monolog": "^3.0",
         "mpdf/mpdf": "^v8.0.10",
         "owasp/csrf-protector-php": "^1.0",
-        "phpmailer/phpmailer": "^6.0",
+        "phpmailer/phpmailer": "^7.0",
         "picqer/php-barcode-generator": "^3.2",
         "respect/validation": "^2.0",
         "servo/fluidxml": "^2.0",