fix: update commonmarker requirement from =0.21.0 to 0.23.1

Updates the requirements on [commonmarker](https://github.com/gjtorikian/commonmarker) to permit the latest version.
- [Release notes](https://github.com/gjtorikian/commonmarker/releases)
- [Commits](gjtorikian/commonmarker@v0.21.0...v0.23.1)

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

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

Author: dependabot[bot]

Gemfile

@@ -3,7 +3,7 @@ source 'https://rubygems.org'
 gem "github-markup", "4.0.0"
 gem "RedCloth", "=4.3.2"
 gem "asciidoctor", "2.0.16"
-gem "commonmarker", "=0.21.0"
+gem "commonmarker", "0.23.1"
 gem "creole", "=0.5.0"
 gem "org-ruby", "=0.9.12"
 gem "rdoc", "6.3.2"