Make ssh-port of servers initially configurable

It looks somehow random that the SSH-port was simply defined in the
configuration of the k3s-setup. It looks somehow "configurable" although
it isn't. Therefore I moved this setting to the correct place in the
terraform-setup.

An important side-note is that this change doesn't make it possible to
_change_ the ssh-port, though. Once decided for an port and I have to
stick to it until I tear down the cluster!

infra/modules/hetzner/kubernetes/outputs.tf

@@ -17,3 +17,7 @@ output "private_network_cidr" {
 output "private_network_nat" {
   value = cidrhost(local.subnet_eu_central, 1)
 }
+
+output "ssh_port" {
+  value = var.ssh_port
+}