Bump org.asciidoctor:asciidoctor-maven-plugin from 2.2.5 to 2.2.6

Bumps [org.asciidoctor:asciidoctor-maven-plugin](https://github.com/asciidoctor/asciidoctor-maven-plugin) from 2.2.5 to 2.2.6.
- [Release notes](https://github.com/asciidoctor/asciidoctor-maven-plugin/releases)
- [Changelog](https://github.com/asciidoctor/asciidoctor-maven-plugin/blob/asciidoctor-maven-plugin-2.2.6/CHANGELOG.adoc)
- [Commits](asciidoctor/asciidoctor-maven-plugin@asciidoctor-maven-plugin-2.2.5...asciidoctor-maven-plugin-2.2.6)

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

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

Author: dependabot[bot]

pom.xml

@@ -44,7 +44,7 @@
         <maven-compiler-plugin.version>3.12.1</maven-compiler-plugin.version>
 
         <!-- Spec document -->
-        <asciidoctor-maven.version>2.2.5</asciidoctor-maven.version>
+        <asciidoctor-maven.version>2.2.6</asciidoctor-maven.version>
         <asciidoctorj-pdf.version>2.3.12</asciidoctorj-pdf.version>
         <maven.build.timestamp.format>MMMM dd, yyyy</maven.build.timestamp.format>
         <revisiondate>${maven.build.timestamp}</revisiondate>