Remove unofficial bare-metal *_networkds variables

* Remove controller_networkds and worker_networkds variables. These
variables were always listed as experimental, unsupported, and excluded
from documentation in anticipation of Container Linux Config snippets
* Use Container Linux Config snippets on bare-metal instead. They
provide safer, more powerful, and more elegant host customization

bare-metal/container-linux/kubernetes/variables.tf

@@ -141,17 +141,3 @@ variable "kernel_args" {
   type        = "list"
   default     = []
 }
-
-# unofficial, undocumented, unsupported, temporary
-
-variable "controller_networkds" {
-  type        = "list"
-  description = "Controller Container Linux config networkd section"
-  default     = []
-}
-
-variable "worker_networkds" {
-  type        = "list"
-  description = "Worker Container Linux config networkd section"
-  default     = []
-}