Bump mrml from 3.0.2 to 3.0.3 in /native/mjml_nif

Bumps [mrml](https://github.com/jdrouet/mrml) from 3.0.2 to 3.0.3.
- [Release notes](https://github.com/jdrouet/mrml/releases)
- [Changelog](https://github.com/jdrouet/mrml/blob/main/changelog.md)
- [Commits](jdrouet/mrml@mrml-v3.0.2...mrml-v3.0.3)

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

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