Replace deprecated datacenter by location for priamry-ips

Hetzner has changed it's API and removed the field `datacenter` from the
primary IPs in favor of `location`. This change reflex this and adjusts
the configuration accordingly. Note, that this change didn't require any
manual state changes. Instead I applied the former plan with the newest
provider once. Hence the provider already treated the fields correctly I
only had to adjust the configuration.
Chapeau Hetzner for this good transition!

See-also: 14da745f Update tofu-resources to their latest versions
Reference: https://docs.hetzner.cloud/changelog#2025-12-16-phasing-out-datacenters

modules/hetzner/kubernetes/main.tf

@@ -2,7 +2,7 @@ resource "hcloud_primary_ip" "ipv4" {
   count = length(var.servers)
 
   name          = "k8s_primary_ipv4_${count.index}"
-  datacenter    = var.servers[count.index].ip_datacenter
+  location      = var.servers[count.index].location
   type          = "ipv4"
   assignee_type = "server"
   auto_delete   = var.auto_delete_primary_ips
@@ -12,7 +12,7 @@ resource "hcloud_primary_ip" "ipv6" {
   count = length(var.servers)
 
   name          = "k8s_primary_ipv6_${count.index}"
-  datacenter    = var.servers[count.index].ip_datacenter
+  location      = var.servers[count.index].location
   type          = "ipv6"
   assignee_type = "server"
   auto_delete   = var.auto_delete_primary_ips

modules/hetzner/kubernetes/variables.tf

@@ -8,9 +8,8 @@ variable "ssh_keys" {
 
 variable "servers" {
   type = list(object({
-    type          = string
-    location      = string
-    ip_datacenter = string
+    type     = string
+    location = string
   }))
 }