Bump swiftmailer/swiftmailer from 6.2.3 to 6.2.4

Bumps [swiftmailer/swiftmailer](https://github.com/swiftmailer/swiftmailer) from 6.2.3 to 6.2.4.
- [Release notes](https://github.com/swiftmailer/swiftmailer/releases)
- [Changelog](https://github.com/swiftmailer/swiftmailer/blob/master/CHANGES)
- [Commits](swiftmailer/swiftmailer@v6.2.3...v6.2.4)

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