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] <[email protected]>

grails-docs/build.gradle

@@ -12,7 +12,7 @@ dependencies {
             'org.yaml:snakeyaml:2.2',
             "org.codehaus.groovy:groovy-ant:$groovyVersion"
 
-    api 'org.asciidoctor:asciidoctorj:2.5.12'
+    api 'org.asciidoctor:asciidoctorj:2.5.13'
     api('org.xhtmlrenderer:core-renderer:8.0') {
         exclude group: 'bouncycastle', module:'bcprov-jdk14'
     }