Enable RedundantModifier Checkstyle check

core/src/main/java/hudson/Functions.java

@@ -1450,7 +1450,7 @@ public class Functions {
     private static class ThreadSorterBase {
         protected Map<Long,String> map = new HashMap<>();
 
-        public ThreadSorterBase() {
+        ThreadSorterBase() {
             ThreadGroup tg = Thread.currentThread().getThreadGroup();
             while (tg.getParent() != null) tg = tg.getParent();
             Thread[] threads = new Thread[tg.activeCount()*2];