Bump org.asciidoctor:asciidoctorj from 2.5.10 to 2.5.12

Bumps [org.asciidoctor:asciidoctorj](https://github.com/asciidoctor/asciidoctorj) from 2.5.10 to 2.5.12.
- [Release notes](https://github.com/asciidoctor/asciidoctorj/releases)
- [Changelog](https://github.com/asciidoctor/asciidoctorj/blob/v2.5.12/CHANGELOG.adoc)
- [Commits](asciidoctor/asciidoctorj@v2.5.10...v2.5.12)

---
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>

spec/pom.xml

@@ -34,7 +34,7 @@
     <properties>
         <site.output.dir>${project.build.directory}/staging</site.output.dir>
         <maven.site.skip>true</maven.site.skip>
-        <asciidoctorj.version>2.5.10</asciidoctorj.version>
+        <asciidoctorj.version>2.5.12</asciidoctorj.version>
         <asciidoctorj.pdf.version>2.3.9</asciidoctorj.pdf.version>
         <jruby.version>9.3.13.0</jruby.version>
         <!-- status: DRAFT, BETA, etc., or blank for final -->