build(deps): bump gatsby from 4.6.2 to 4.9.0 in /docs (golangci#2631)

Bumps [gatsby](https://github.com/gatsbyjs/gatsby) from 4.6.2 to 4.9.0.
- [Release notes](https://github.com/gatsbyjs/gatsby/releases)
- [Changelog](https://github.com/gatsbyjs/gatsby/blob/master/CHANGELOG.md)
- [Commits](https://github.com/gatsbyjs/gatsby/compare/gatsby@4.6.2...gatsby@4.9.0)

---
updated-dependencies:
- dependency-name: gatsby
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>