Merge pull request #4124 from michelleN/security-email

update security vulnerability email

CONTRIBUTING.md

@@ -7,7 +7,7 @@ The Kubernetes Helm project accepts contributions via GitHub pull requests. This
 Most of the time, when you find a bug in Helm, it should be reported
 using [GitHub issues](https://github.com/kubernetes/helm/issues). However, if
 you are reporting a _security vulnerability_, please email a report to
-[helm-security@deis.com](mailto:helm-security@deis.com). This will give
+[cncf-kubernetes-helm-security@lists.cncf.io](mailto:cncf-kubernetes-helm-security@lists.cncf.io). This will give
 us a chance to try to fix the issue before it is exploited in the wild.
 
 ## Contributor License Agreements