The `config.yml` document for *kitchen* contains several "secret" values
(e.g. passwords to Nextcloud, MQTT, etc.). We don't want to commit
these to the Git repository, of course, but as long as Kustomize expects
to find the `config.yml` file, we won't be able to manage the
application with Argo CD. Ultimately, *kitchen* needs to be modified to
be able to read secrets separately from config, but until then, we will
have to avoid managing `config.yml` with Kustomize.