Util: Remove ST2 timers from queue on cancel

May reduce memory usage a little

core/java/src/net/i2p/util/SimpleTimer2.java

@@ -113,6 +113,7 @@ public class SimpleTimer2 {
     private static class CustomScheduledThreadPoolExecutor extends ScheduledThreadPoolExecutor {
         public CustomScheduledThreadPoolExecutor(int threads, ThreadFactory factory) {
              super(threads, factory);
+             setRemoveOnCancelPolicy(true);
         }
 
         @Override