Merge pull request #463 from jenkinsci/dependabot/maven/org.asciidoctor-asciidoctorj-pdf-2.3.9

Bump asciidoctorj-pdf from 2.3.4 to 2.3.9

Author: jglick

pom.xml

@@ -195,7 +195,7 @@
       <id>pdfs</id>
       <properties>
         <asciidoctor.maven.plugin.version>2.2.3</asciidoctor.maven.plugin.version>
-        <asciidoctorj.pdf.version>2.3.4</asciidoctorj.pdf.version>
+        <asciidoctorj.pdf.version>2.3.9</asciidoctorj.pdf.version>
         <asciidoctorj.version>2.5.8</asciidoctorj.version>
         <jruby.version>9.4.2.0</jruby.version>
       </properties>