Changes upgrades clusters to use only us based regions

build/terraform/upgrade/module.tf

@@ -38,8 +38,8 @@ variable "kubernetes_versions" {
   description = "Create upgrade test clusters with these k8s versions in these regions"
   type        = map(list(string))
   default     = {
-    "1.29" = ["europe-west1", "RAPID"]
-    "1.30" = ["asia-east1", "RAPID"]
+    "1.29" = ["us-west1", "RAPID"]
+    "1.30" = ["us-central1", "RAPID"]
     "1.31" = ["us-east1", "RAPID"]
     //1.32" = ["us-west1", "RAPID"]
     //
@@ -56,9 +56,9 @@ variable "kubernetes_versions" {
     //   should be using the region of the previous 1.{N-3} - this region will become
     //   unused.
     //
-    // Rationale: We cycle the regions us-east1 -> us-west1 -> europe-west1 -> asia-east1 -> us-east1
-    // as versions are added, using 4 regions so that the PR adding 1.{N} is in a unique region to
-    // 1.{N-3} .. 1.{N-1}, meaning versions never need to share a region in CI.
+    // Rationale: We cycle the regions us-east1 -> us-west1 -> us-central1 -> us-east1
+    // as versions are added, using 3 regions so that the PR adding 1.{N} is in a unique region to
+    // 1.{N-2} .. 1.{N-1}, meaning versions never need to share a region in CI.
   }
 }