Bump symfony/mailer from 6.4.4 to 6.4.6 in /app

Bumps [symfony/mailer](https://github.com/symfony/mailer) from 6.4.4 to 6.4.6.
- [Release notes](https://github.com/symfony/mailer/releases)
- [Changelog](https://github.com/symfony/mailer/blob/7.0/CHANGELOG.md)
- [Commits](symfony/mailer@v6.4.4...v6.4.6)

---
updated-dependencies:
- dependency-name: symfony/mailer
  dependency-type: indirect
  update-type: version-update:semver-patch
...

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