GROOVY-11349: Bump asciidoctorj pdf to 2.3.15
diff --git a/versions.properties b/versions.properties
index 7f3ab21..e9eb903 100644
--- a/versions.properties
+++ b/versions.properties
@@ -16,7 +16,7 @@
 ant=1.10.14
 asciidoctorj=2.5.11
 asciidoctorDiagram=2.3.0
-asciidoctorPdf=2.3.14
+asciidoctorPdf=2.3.15
 asciidoctorGroovyDsl=2.0.2
 asm=9.7
 antlr4=4.13.1.3