Bump nokogiri from 1.13.3 to 1.13.4 in /docs (#367)

Bumps [nokogiri](https://github.com/sparklemotion/nokogiri) from 1.13.3 to 1.13.4.
- [Release notes](https://github.com/sparklemotion/nokogiri/releases)
- [Changelog](https://github.com/sparklemotion/nokogiri/blob/v1.13.4/CHANGELOG.md)
- [Commits](https://github.com/sparklemotion/nokogiri/compare/v1.13.3...v1.13.4)

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

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

docs/Gemfile.lock

@@ -231,7 +231,7 @@ GEM
       jekyll-seo-tag (~> 2.1)
     minitest (5.15.0)
     multipart-post (2.1.1)
-    nokogiri (1.13.3-x86_64-linux)
+    nokogiri (1.13.4-x86_64-linux)
       racc (~> 1.4)
     octokit (4.22.0)
       faraday (>= 0.9)