make UserStateSMSSynchronizer package-private

This class wasn't intented to be public, marking it as package-private.

Author: jkasten2

OneSignalSDK/onesignal/src/main/java/com/onesignal/UserStateSMSSynchronizer.java

@@ -5,7 +5,7 @@
 import java.util.ArrayList;
 import java.util.List;
 
-public class UserStateSMSSynchronizer extends UserStateSecondaryChannelSynchronizer {
+class UserStateSMSSynchronizer extends UserStateSecondaryChannelSynchronizer {
 
     UserStateSMSSynchronizer() {
         super(OneSignalStateSynchronizer.UserStateSynchronizerType.SMS);