Fixes wrong completionHandler call

In case of iOS 10+ the call to grant permission was made outside of the `requestAuthorizationWithOptions(..)` block and returned immediately with `PermissionStatusGranted` which leads to a totally useless permission request.

permission_handler/ios/Classes/strategies/NotificationPermissionStrategy.m

@@ -37,7 +37,11 @@
           completionHandler(PermissionStatusDenied);
           return;
         }
+
+        [[UIApplication sharedApplication] registerForRemoteNotifications];
+        completionHandler(PermissionStatusGranted);
       }];
+
     } else {
       UIUserNotificationType notificationTypes = 0;
       notificationTypes |= UIUserNotificationTypeSound;
@@ -45,9 +49,10 @@
       notificationTypes |= UIUserNotificationTypeBadge;
       UIUserNotificationSettings *settings = [UIUserNotificationSettings settingsForTypes:notificationTypes categories:nil];
       [[UIApplication sharedApplication] registerUserNotificationSettings:settings];
-    }
+
       [[UIApplication sharedApplication] registerForRemoteNotifications];
       completionHandler(PermissionStatusGranted);
+    }
   });
 }