Remove duplicate register call

Summary:Hello!

As described in #3288, the `PushNotificationsIOS` `register` callback fires twice.  See that issue for discussion.

There wasn't any feedback on a proposed PR, so this is the first effort.  This change does make the register callback act as expected on my device.  I can make any changes necessary.

Thanks!
Closes https://github.com/facebook/react-native/pull/6111

Differential Revision: D2970806

Pulled By: nicklockwood

fb-gh-sync-id: a8d0b53210f85cc24b4befdb0e90af46512fa4fb
shipit-source-id: a8d0b53210f85cc24b4befdb0e90af46512fa4fb

Libraries/PushNotificationIOS/RCTPushNotificationManager.m

@@ -182,7 +182,6 @@ RCT_EXPORT_METHOD(requestPermissions:(NSDictionary *)permissions)
     UIUserNotificationSettings *notificationSettings =
       [UIUserNotificationSettings settingsForTypes:(NSUInteger)types categories:nil];
     [app registerUserNotificationSettings:notificationSettings];
-    [app registerForRemoteNotifications];
   } else {
     [app registerForRemoteNotificationTypes:(NSUInteger)types];
   }