Bump org.asciidoctor:asciidoctorj from 2.5.12 to 2.5.13

Bumps [org.asciidoctor:asciidoctorj](https://github.com/asciidoctor/asciidoctorj) from 2.5.12 to 2.5.13.
- [Release notes](https://github.com/asciidoctor/asciidoctorj/releases)
- [Changelog](https://github.com/asciidoctor/asciidoctorj/blob/v2.5.13/CHANGELOG.adoc)
- [Commits](asciidoctor/asciidoctorj@v2.5.12...v2.5.13)

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

Signed-off-by: dependabot[bot] <support@github.com>

specification/pom.xml

@@ -48,7 +48,7 @@
         <maven.site.skip>true</maven.site.skip>
 
         <asciidoctor.maven.plugin.version>3.0.0</asciidoctor.maven.plugin.version>
-        <asciidoctorj.version>2.5.12</asciidoctorj.version>
+        <asciidoctorj.version>2.5.13</asciidoctorj.version>
         <asciidoctorj.pdf.version>2.3.15</asciidoctorj.pdf.version>
         <jruby.version>9.4.7.0</jruby.version>