.github: remove stackoverflow from support issue template

The upstream project isn't officially tied to StackOverflow and we direct
folks to Discuss now.

Author: nikhita

.github/ISSUE_TEMPLATE/support.md

@@ -10,7 +10,8 @@ STOP -- PLEASE READ!
 
 GitHub is not the right place for support requests.
 
-If you're looking for help, check [Stack Overflow](https://stackoverflow.com/questions/tagged/kubernetes) and the [troubleshooting guide](https://kubernetes.io/docs/tasks/debug-application-cluster/troubleshooting/).
+If you're looking for help, check the [troubleshooting guide](https://kubernetes.io/docs/tasks/debug-application-cluster/troubleshooting/)
+or our [Discussion Forums](https://discuss.kubernetes.io).
 
 You can also post your question on the [Kubernetes Slack](http://slack.k8s.io/) or the [Discuss Kubernetes](https://discuss.kubernetes.io/) forum.