Call "flushState" after calling "contentHandler" in the NSE.

Summary:
This differential places a call to "flushState" after a call to "contentHandler" to handle the possibility that the NSE restarts notification processing
before calling "contentHandler"

Test Plan:
Add ling with logging just after the line that calls "contentHandler". Build iOS app and sends some notifications ensure that logging line is called at
least every 4 - 5 notifications.

Reviewers: tomek, ashoat

Reviewed By: ashoat

Subscribers: wyilio

Differential Revision: https://phab.comm.dev/D9822

native/ios/NotificationService/NotificationService.mm

@@ -221,13 +221,13 @@ - (void)didReceiveNotificationRequest:(UNNotificationRequest *)request
     return;
   }
 
+  [self callContentHandlerForKey:contentHandlerKey
+                     withContent:publicUserContent];
+
   if (decryptionExecuted) {
     comm::NotificationsCryptoModule::flushState(
         std::move(statefulDecryptResultPtr), callingProcessName);
   }
-
-  [self callContentHandlerForKey:contentHandlerKey
-                     withContent:publicUserContent];
 }
 
 - (void)serviceExtensionTimeWillExpire {