chore(deps): bump next from 13.4.8 to 13.4.9 in /docs

Bumps [next](https://github.com/vercel/next.js) from 13.4.8 to 13.4.9.
- [Release notes](https://github.com/vercel/next.js/releases)
- [Changelog](https://github.com/vercel/next.js/blob/canary/release.js)
- [Commits](vercel/next.js@v13.4.8...v13.4.9)

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

Signed-off-by: dependabot[bot] <[email protected]>