Bump PMD from 7.18.0 to 7.21.0 for checks (#332)

Author: adangel

pom.xml

@@ -78,7 +78,7 @@
 
         <pmd.build-tools.version>36</pmd.build-tools.version>
         <pmd.plugin.version>3.28.0</pmd.plugin.version>
-        <pmd.check.version>7.18.0</pmd.check.version>
+        <pmd.check.version>7.21.0</pmd.check.version>
 
         <jflex-output>${project.build.directory}/generated-sources/jflex</jflex-output>