Namespace is relevant in helm lint [#8]

...Or at least, the namespace is passed around in helm's linting code. I
haven't proven that there's a case where omitting the namespace can
cause a linting problem, but I've seen enough to go ahead and document
the setting.

docs/lint_settings.yml

@@ -32,5 +32,4 @@ steps:
       repos: "eDeath=https://github.com/bug/e-death,idMaker=https://github.com/nmarks/id-maker"
 
       # Give the --namespace flag to all helm commands.
-      # TODO: I don't think this setting has any effect on linting; should it be documented?
       namespace: my_kube_subset