2i2c-uk: upgrade k8s 1.24 -> 1.27, and use pd-balanced disks

terraform/gcp/projects/2i2c-uk.tfvars

@@ -1,10 +1,17 @@
 prefix     = "two-eye-two-see-uk"
 project_id = "two-eye-two-see-uk"
 
-zone   = "europe-west2-b"
-region = "europe-west2"
+zone             = "europe-west2-b"
+region           = "europe-west2"
+regional_cluster = true
 
-core_node_machine_type = "n1-highmem-4"
+k8s_versions = {
+  min_master_version : "1.27.4-gke.900",
+  core_nodes_version : "1.27.4-gke.900",
+  notebook_nodes_version : "1.27.4-gke.900",
+}
+
+core_node_machine_type = "n2-highmem-4"
 enable_network_policy  = true
 
 # Setup a filestore for in-cluster NFS
@@ -15,7 +22,7 @@ notebook_nodes = {
   "user" : {
     min : 0,
     max : 20,
-    machine_type : "n1-highmem-4"
+    machine_type : "n2-highmem-4"
   },
 }