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-kube-router.yml

@@ -1,11 +1,5 @@
 # See roles/network_plugin/kube-router/defaults/main.yml
 
-# Kube router version
-# Default to v2
-# kube_router_version: "2.0.0"
-# Uncomment to use v1 (Deprecated)
-# kube_router_version: "1.6.0"
-
 # Enables Pod Networking -- Advertises and learns the routes to Pods via iBGP
 # kube_router_run_router: true