Use zones b and c for MIG fixture (#1961)

tests/fixtures/compute-mig-bc.tf

@@ -1,4 +1,4 @@
-# Copyright 2023 Google LLC
+# Copyright 2024 Google LLC
 #
 # Licensed under the Apache License, Version 2.0 (the "License");
 # you may not use this file except in compliance with the License.
@@ -13,23 +13,6 @@
 # limitations under the License.
 
 
-module "compute-mig-a" {
-  source     = "./fabric/modules/compute-vm"
-  project_id = var.project_id
-  zone       = "${var.region}-a"
-  name       = "my-ig-a"
-  network_interfaces = [{
-    network    = var.vpc.self_link
-    subnetwork = var.subnet.self_link
-  }]
-  boot_disk = {
-    initialize_params = {
-      image = "cos-cloud/cos-stable"
-    }
-  }
-  group = { named_ports = {} }
-}
-
 module "compute-mig-b" {
   source     = "./fabric/modules/compute-vm"
   project_id = var.project_id
@@ -46,3 +29,20 @@ module "compute-mig-b" {
   }
   group = { named_ports = {} }
 }
+
+module "compute-mig-c" {
+  source     = "./fabric/modules/compute-vm"
+  project_id = var.project_id
+  zone       = "${var.region}-c"
+  name       = "my-ig-c"
+  network_interfaces = [{
+    network    = var.vpc.self_link
+    subnetwork = var.subnet.self_link
+  }]
+  boot_disk = {
+    initialize_params = {
+      image = "cos-cloud/cos-stable"
+    }
+  }
+  group = { named_ports = {} }
+}