Update to PMD 6.7.0

Author: jgerken

pom.xml

@@ -16,7 +16,7 @@
   <properties>
     <tycho.version>1.1.0</tycho.version>
     <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
-    <pmd.version>6.6.0</pmd.version>
+    <pmd.version>6.7.0</pmd.version>
     <maven-antrun-plugin.version>1.8</maven-antrun-plugin.version>
   </properties>