Let checkstyle prevent redundant modifiers in the future

etc/checkstyle/checkstyle.xml

@@ -20,6 +20,7 @@
 
 		<!-- Coding -->
 		<module name="EmptyStatementCheck" />
+		<module name="RedundantModifier" />
 
 		<!-- Imports -->
 		<module name="UnusedImportsCheck">