docs: Fix offline-environment.md to add 'v' prefix of some versions (#12166)

* docs: Fix offline-environment.md to add 'v' prefix of some versions

Now some version variables (kube_version, etcd_version, etc) don't have 'v' prefix,
so you need to add 'v' prefix to download URLs.

* fix: Fix offline.yml to add 'v' prefix of some versions