build(deps): bump mail-parser from 4.1.4 to 4.2.1 in /mail (#55)

Bumps [mail-parser](https://github.com/SpamScope/mail-parser) from 4.1.4 to 4.2.1.
- [Release notes](https://github.com/SpamScope/mail-parser/releases)
- [Commits](SpamScope/mail-parser@4.1.4...4.2.1)

---
updated-dependencies:
- dependency-name: mail-parser
  dependency-version: 4.2.1
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

Author: dependabot[bot]

mail/requirements.txt

@@ -1 +1 @@
-mail-parser==4.1.4
+mail-parser==4.2.1