Remove versions from inventory sample (#12164)

The recommended usage of kubespray is to use the default versions.
So putting them in inventory/sample is not really very helpful, and
causes:
- churn (keeping the inventory/sample up to date)
- support issues (mismatch between defaults and sample inventory)

Remove all concrete versions from the inventory sample.

inventory/sample/group_vars/k8s_cluster/k8s-net-cilium.yml

@@ -1,6 +1,4 @@
 ---
-# cilium_version: "1.15.9"
-
 # Log-level
 # cilium_debug: false