Deprecated function getException() in RedirectSubscriber

Thanks for the patch @chaimaariz,
In Drupal 10, I'm also getting the same error. This patch fixed it.

https://github.com/ekino/EkinoNewRelicBundle/issues/237

Starting from Symfony 4.4, GetResponseForExceptionEvent::getException is deprecated. It should be replaced with getThrowable.

Also GetResponseForExceptionEvent is deprecated, and should be replaced with ExceptionEvent