Needed to change defaults again for getStringSet

* `OneSignalCacheCleaner.java` was rearranged a bit and it caused conflicts
* `OSInAppMessageRepository.java` now has those correct changes an the default was flipped `OSUtils.<String>newConcurrentSet()` to `null`

Author: mikechoch

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

@@ -179,12 +179,12 @@ private void cleanInAppMessageIds(Set<String> oldMessageIds) {
             Set<String> dismissedMessages = OneSignalPrefs.getStringSet(
                     OneSignalPrefs.PREFS_ONESIGNAL,
                     OneSignalPrefs.PREFS_OS_DISMISSED_IAMS,
-                    OSUtils.<String>newConcurrentSet());
+                    null);
 
             Set<String> impressionedMessages = OneSignalPrefs.getStringSet(
                     OneSignalPrefs.PREFS_ONESIGNAL,
                     OneSignalPrefs.PREFS_OS_IMPRESSIONED_IAMS,
-                    OSUtils.<String>newConcurrentSet());
+                    null);
 
             if (dismissedMessages != null && dismissedMessages.size() > 0) {
                 dismissedMessages.removeAll(oldMessageIds);
@@ -218,7 +218,7 @@ private void cleanInAppMessageClickedClickIds(Set<String> oldClickedClickIds) {
             Set<String> clickedClickIds = OneSignalPrefs.getStringSet(
                     OneSignalPrefs.PREFS_ONESIGNAL,
                     OneSignalPrefs.PREFS_OS_CLICKED_CLICK_IDS_IAMS,
-                    OSUtils.<String>newConcurrentSet());
+                    null);
 
             if (clickedClickIds != null && clickedClickIds.size() > 0) {
                 clickedClickIds.removeAll(oldClickedClickIds);