Bump @rollup/plugin-babel from 5.3.0 to 6.0.3

Bumps [@rollup/plugin-babel](https://github.com/rollup/plugins/tree/HEAD/packages/babel) from 5.3.0 to 6.0.3.
- [Release notes](https://github.com/rollup/plugins/releases)
- [Changelog](https://github.com/rollup/plugins/blob/master/packages/babel/CHANGELOG.md)
- [Commits](https://github.com/rollup/plugins/commits/babel-v6.0.3/packages/babel)

---
updated-dependencies:
- dependency-name: "@rollup/plugin-babel"
  dependency-type: direct:development
  update-type: version-update:semver-major
...

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Author: dependabot[bot]