Bump mjml from 4.15.2 to 4.15.3

Bumps [mjml](https://github.com/mjmlio/mjml/tree/HEAD/packages/mjml) from 4.15.2 to 4.15.3.
- [Release notes](https://github.com/mjmlio/mjml/releases)
- [Commits](https://github.com/mjmlio/mjml/commits/v4.15.3/packages/mjml)

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

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Author: dependabot[bot]