Reference to a potentially unmaintained project (coredns/policy#kubernetes-metadata-multi-tenancy-policy.)

The project [coredns/policy#kubernetes-metadata-multi-tenancy-policy.](https://github.com/coredns/policy#kubernetes-metadata-multi-tenancy-policy.) has not been pushed to since 2023-03-22. Please check if the project is still maintained.