Bump nokogiri from 1.12.5 to 1.13.6 in /docs (#295)

Bumps [nokogiri](https://github.com/sparklemotion/nokogiri) from 1.12.5 to 1.13.6.
- [Release notes](https://github.com/sparklemotion/nokogiri/releases)
- [Changelog](https://github.com/sparklemotion/nokogiri/blob/main/CHANGELOG.md)
- [Commits](sparklemotion/nokogiri@v1.12.5...v1.13.6)

---
updated-dependencies:
- dependency-name: nokogiri
  dependency-type: direct:production
...

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

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

docs/Gemfile.lock

@@ -105,7 +105,7 @@ GEM
     mercenary (0.4.0)
     minitest (5.15.0)
     multipart-post (2.2.3)
-    nokogiri (1.12.5-x86_64-linux)
+    nokogiri (1.13.6-x86_64-linux)
       racc (~> 1.4)
     octokit (4.25.1)
       faraday (>= 1, < 3)