Synchronization no longer required

Author: aurimasc

com.unity.mobile.notifications/Runtime/Android/Plugins/com/unity/androidnotifications/UnityNotificationManager.java

@@ -395,12 +395,10 @@ void performNotificationHousekeeping(Set<String> ids) {
         Log.d(TAG_UNITY, "Checking for invalid notification IDs still hanging around");
 
         Set<String> invalid = findInvalidNotificationIds(ids);
-        synchronized (UnityNotificationManager.class) {
-            Set<String> currentIds = new HashSet<>(ids);
-            for (String id : invalid) {
-                currentIds.remove(id);
-                mScheduledNotifications.remove(id);
-            }
+        Set<String> currentIds = new HashSet<>(ids);
+        for (String id : invalid) {
+            currentIds.remove(id);
+            mScheduledNotifications.remove(id);
         }
 
         // in case we have saved intents, clear them