[bug]: v0.0.12 helm chart now requires that you pass in your own namespace

In https://github.com/coder/coder-logstream-kube/pull/124 you now must pass in your own namespace as a parameter to the helm chart if you don't want to create a `ClusterRole` and `ClusterRoleBinding`. This is rough from a GitOps perspective, because it means that you have two choices (_in an environment where applications are not allowed to create cluster-scoped resources_):

1. You create `values..yaml` files where you set `namespaces: [ my-coder-ns ]` and launch the application with custom values files for each namespace you put it in.
2. When you launch the application you pass in `--set namespaces=...`

In my opinion, if `namespaces` is not set, then there should be a simple setting of `rbacScope: ` ... and if it is set to `namespace` then the RBAC permissions created with `Role/RoleBindings` (and `NAMESPACES=${{ .Release.Namespace}}` is set as an env variable). If it is set to `cluster`, then you create `ClusterRole/ClusterRoleBindings`.