Bump nokogiri from 1.13.4 to 1.13.6 in /docs (#1965)

Bumps [nokogiri](https://github.com/sparklemotion/nokogiri) from 1.13.4 to 1.13.6.
- [Release notes](https://github.com/sparklemotion/nokogiri/releases)
- [Changelog](https://github.com/sparklemotion/nokogiri/blob/main/CHANGELOG.md)
- [Commits](https://github.com/sparklemotion/nokogiri/compare/v1.13.4...v1.13.6)

---
updated-dependencies:
- dependency-name: nokogiri
  dependency-type: indirect
...
Signed-off-by: Ndependabot[bot] <support@github.com>
Co-authored-by: Ndependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

docs/Gemfile.lock

@@ -14,7 +14,7 @@ GEM
       execjs
     coffee-script-source (1.11.1)
     colorator (1.1.0)
-    commonmarker (0.23.4)
+    commonmarker (0.17.13)
       ruby-enum (~> 0.5)
     concurrent-ruby (1.1.10)
     dnsruby (1.61.9)
@@ -240,7 +240,7 @@ GEM
       jekyll-sitemap (~> 1.3)
     minitest (5.15.0)
     multipart-post (2.1.1)
-    nokogiri (1.13.4)
+    nokogiri (1.13.6)
       mini_portile2 (~> 2.8.0)
       racc (~> 1.4)
     octokit (4.22.0)