Bump nokogiri from 1.13.7 to 1.13.9 in /docs (#408)

Bumps [nokogiri](https://github.com/sparklemotion/nokogiri) from 1.13.7 to 1.13.9.
- [Release notes](https://github.com/sparklemotion/nokogiri/releases)
- [Changelog](https://github.com/sparklemotion/nokogiri/blob/main/CHANGELOG.md)
- [Commits](sparklemotion/nokogiri@v1.13.7...v1.13.9)

---
updated-dependencies:
- dependency-name: nokogiri
  dependency-type: indirect
...

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

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

Author: dependabot[bot]

docs/Gemfile.lock

@@ -215,7 +215,7 @@ GEM
       jekyll-feed (~> 0.9)
       jekyll-seo-tag (~> 2.1)
     minitest (5.16.2)
-    nokogiri (1.13.7-x86_64-linux)
+    nokogiri (1.13.9-x86_64-linux)
       racc (~> 1.4)
     octokit (4.25.1)
       faraday (>= 1, < 3)