build(deps): bump asciidoctorj-diagram from 2.2.7 to 2.2.8 (#934)

Bumps [asciidoctorj-diagram](https://github.com/asciidoctor/asciidoctorj-diagram) from 2.2.7 to 2.2.8.
- [Release notes](https://github.com/asciidoctor/asciidoctorj-diagram/releases)
- [Commits](https://github.com/asciidoctor/asciidoctorj-diagram/commits/v2.2.8)

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

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

pom.xml

@@ -157,7 +157,7 @@
     <!-- Site properties -->
     <asciidoctor.maven.plugin.version>2.2.3</asciidoctor.maven.plugin.version>
     <asciidoctorj.version>2.5.8</asciidoctorj.version>
-    <asciidoctorj.diagram.version>2.2.7</asciidoctorj.diagram.version>
+    <asciidoctorj.diagram.version>2.2.8</asciidoctorj.diagram.version>
 
     <skip-code-generation-tests>true</skip-code-generation-tests>
     <enable-all-tests>false</enable-all-tests>