reword confusing etcd download url comment (#9686)

It is quite confusing that there's an all-caps, bolded comment that seems to imply that `etcd_download_url` is relevant only when not using host-based deployment. The opposite is true: of course the artifact download URL is relevant and required for host-based etcd.

Perhaps the entire comment can be read in a different way, and should perhaps be reworded entirely, cf. https://github.com/kubernetes-sigs/kubespray/blob/374438a3d631e98b34db4433d972fb4a221c0505/docs/offline-environment.md?plain=1#L38

Removing the "**DON'T**" matches the way the other comments in this file are written and matches my personal interpretation.