Update README.md

README.md

@@ -223,7 +223,7 @@ Edit `AppDelegate.m`:
 +   [RNFIRMessaging willPresentNotification:notification withCompletionHandler:completionHandler];
 + }
 +
-+ - (void)userNotificationCenter:(UNUserNotificationCenter *)center didReceiveNotificationResponse:(UNNotificationResponse *)response withCompletionHandler:(void (^)())completionHandler
++ - (void)userNotificationCenter:(UNUserNotificationCenter *)center didReceiveNotificationResponse:(UNNotificationResponse *)response withCompletionHandler:(void (^)(void))completionHandler
 + {
 +   [RNFIRMessaging didReceiveNotificationResponse:response withCompletionHandler:completionHandler];
 + }