add rbac to all linkerd configs

rbac is enabled by default on newer versions of kubernetes. we should make this part of the default kubernetes linkerd config.

this commit added rbac to the default linkerd config, but did not update any docs around it:
https://github.com/linkerd/linkerd-examples/commit/8967603cf8d0b0f4983d845f0a57beb8d8cad9c2

Start by reviewing the default Kubernetes Linkerd configuration and the referenced commit 8967603cf8d0b0f4983d845f0a57beb8d8cad9c2. Identify every Linkerd config that needs RBAC, then verify that the default configurations consistently include it and that the related documentation is updated.

Written by the indexing model from the issue text.