[Security] Bump symfony/mime from 4.3.3 to 4.4.0

Bumps [symfony/mime](https://github.com/symfony/mime) from 4.3.3 to 4.4.0. **This update includes a security fix.**
- [Release notes](https://github.com/symfony/mime/releases)
- [Changelog](https://github.com/symfony/mime/blob/master/CHANGELOG.md)
- [Commits](symfony/mime@v4.3.3...v4.4.0)

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