Update support.md

Author: andyzhangx

.github/ISSUE_TEMPLATE/support.md

@@ -9,7 +9,7 @@ STOP -- PLEASE READ!
 
 GitHub is not the right place for support requests.
 
-If you're looking for help, post your question on the [Kubernetes Slack ](http://slack.k8s.io/) Sig-AZURE Channel.
+If you're looking for help, post your question on the [provider-azure slack channel](https://kubernetes.slack.com/messages/provider-azure).
 
 If the matter is security related, please disclose it privately via https://kubernetes.io/security/.
 -->