build(deps-dev): bump @wordpress/eslint-plugin from 21.1.2 to 21.4.0

Bumps [@wordpress/eslint-plugin](https://github.com/WordPress/gutenberg/tree/HEAD/packages/eslint-plugin) from 21.1.2 to 21.4.0.
- [Release notes](https://github.com/WordPress/gutenberg/releases)
- [Changelog](https://github.com/WordPress/gutenberg/blob/trunk/packages/eslint-plugin/CHANGELOG.md)
- [Commits](https://github.com/WordPress/gutenberg/commits/@wordpress/eslint-plugin@21.4.0/packages/eslint-plugin)

---
updated-dependencies:
- dependency-name: "@wordpress/eslint-plugin"
  dependency-type: direct:development
  update-type: version-update:semver-minor
...

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