remove duplicated var

inventory/sample/group_vars/all/all.yml

@@ -38,10 +38,6 @@ bin_dir: /usr/local/bin
 ## modules.
 #kubelet_load_modules: false
 
-## Internal network total size. This is the prefix of the
-## entire network. Must be unused in your environment.
-#kube_network_prefix: 18
-
 ## With calico it is possible to distributed routes with border routers of the datacenter.
 ## Warning : enabling router peering will disable calico's default behavior ('node mesh').
 ## The subnets of each nodes will be distributed by the datacenter router