feat(privatek8s): minimum count for autoscalling to 1 for spot instan…

…ces nodes (#609)

as per jenkins-infra/helpdesk#3918

for the ARM64 node the price for 1 node all month is around 14$:

![image](https://github.com/jenkins-infra/azure/assets/95630726/dcf8a6fc-7432-4710-b7f8-f6fb24b2864d)

for the intel node the price for 1 node all month is around 33$:

![image](https://github.com/jenkins-infra/azure/assets/95630726/93fd25e9-426a-4a7a-a703-b4052498ce64)

privatek8s.tf

@@ -145,7 +145,7 @@ resource "azurerm_kubernetes_cluster_node_pool" "infraciarm64" {
   orchestrator_version  = local.kubernetes_versions["privatek8s"]
   kubernetes_cluster_id = azurerm_kubernetes_cluster.privatek8s.id
   enable_auto_scaling   = true
-  min_count             = 0
+  min_count             = 1
   max_count             = 10
   zones                 = [1]
   vnet_subnet_id        = data.azurerm_subnet.privatek8s_tier.id