Bump phpmailer/phpmailer from 6.6.3 to 6.6.4 in /web/inc (hestiacp#2891)

Bumps [phpmailer/phpmailer](https://github.com/PHPMailer/PHPMailer) from 6.6.3 to 6.6.4.
- [Release notes](https://github.com/PHPMailer/PHPMailer/releases)
- [Changelog](https://github.com/PHPMailer/PHPMailer/blob/master/changelog.md)
- [Commits](PHPMailer/PHPMailer@v6.6.3...v6.6.4)

---
updated-dependencies:
- dependency-name: phpmailer/phpmailer
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

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

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Author: dependabot[bot]