Bump org.asciidoctor:asciidoctorj-diagram from 2.2.3 to 2.3.1

Bumps [org.asciidoctor:asciidoctorj-diagram](https://github.com/asciidoctor/asciidoctorj-diagram) from 2.2.3 to 2.3.1.
- [Release notes](https://github.com/asciidoctor/asciidoctorj-diagram/releases)
- [Commits](asciidoctor/asciidoctorj-diagram@v2.2.3...v2.3.1)

---
updated-dependencies:
- dependency-name: org.asciidoctor:asciidoctorj-diagram
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

pom.xml

@@ -948,7 +948,7 @@
             <properties>
                 <asciidoctor.maven.plugin.version>2.2.2</asciidoctor.maven.plugin.version>
                 <asciidoctorj.version>2.5.6</asciidoctorj.version>
-                <asciidoctorj.diagram.version>2.2.3</asciidoctorj.diagram.version>
+                <asciidoctorj.diagram.version>2.3.1</asciidoctorj.diagram.version>
                 <jruby.version>9.3.4.0</jruby.version>
             </properties>