Bump commonmarker from 0.23.8 to 0.23.9 in /docs (#657)

Bumps [commonmarker](https://github.com/gjtorikian/commonmarker) from 0.23.8 to 0.23.9.
- [Release notes](https://github.com/gjtorikian/commonmarker/releases)
- [Changelog](https://github.com/gjtorikian/commonmarker/blob/main/CHANGELOG.md)
- [Commits](gjtorikian/commonmarker@v0.23.8...v0.23.9)

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

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[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 (0.23.8)
+    commonmarker (0.23.9)
     concurrent-ruby (1.2.0)
     dnsruby (1.61.9)
       simpleidn (~> 0.1)