build(deps): bump chef-utils from 17.8.25 to 17.9.18 in /docs

Bumps [chef-utils](https://github.com/chef/chef) from 17.8.25 to 17.9.18.
- [Release notes](https://github.com/chef/chef/releases)
- [Changelog](https://github.com/chef/chef/blob/main/CHANGELOG.md)
- [Commits](https://github.com/chef/chef/compare/v17.8.25...v17.9.18)

---
updated-dependencies:
- dependency-name: chef-utils
  dependency-type: indirect
  update-type: version-update:semver-minor
...

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