GROOVY-9624: Bump Codenarc to 1.6
diff --git a/gradle/quality.gradle b/gradle/quality.gradle
index fa7b9a9..6b07cf8 100644
--- a/gradle/quality.gradle
+++ b/gradle/quality.gradle
@@ -42,7 +42,7 @@
 
     dependencies {
         checkstyle "com.puppycrawl.tools:checkstyle:$checkstyleVersion"
-        codenarc "org.codenarc:CodeNarc:1.5"
+        codenarc "org.codenarc:CodeNarc:1.6"
         spotbugs "com.github.spotbugs:spotbugs:$spotbugsVersion"
         if (proj.name.contains('jaxb') && JavaVersion.current().isJava9Compatible()) {
             spotbugs 'javax.xml.bind:jaxb-api:2.3.0'