build(deps): bump remark-lint-first-heading-level from 3.1.2 to 4.0.0

Bumps [remark-lint-first-heading-level](https://github.com/remarkjs/remark-lint) from 3.1.2 to 4.0.0.
- [Release notes](https://github.com/remarkjs/remark-lint/releases)
- [Changelog](https://github.com/remarkjs/remark-lint/blob/4.0.0/history.md)
- [Commits](https://github.com/remarkjs/remark-lint/commits/4.0.0)

---
updated-dependencies:
- dependency-name: remark-lint-first-heading-level
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <support@github.com>