Remove unnecessary synchronization in SmackReater.schedule()

The DelayQueue 'scheduledActions' is already thread-safe.

smack-core/src/main/java/org/jivesoftware/smack/SmackReactor.java

@@ -149,9 +149,7 @@ public class SmackReactor {
         long releaseTimeEpoch = System.currentTimeMillis() + unit.toMillis(delay);
         Date releaseTimeDate = new Date(releaseTimeEpoch);
         ScheduledAction scheduledAction = new ScheduledAction(runnable, releaseTimeDate, this);
-        synchronized (scheduledActions) {
         scheduledActions.add(scheduledAction);
-        }
         return scheduledAction;
     }