chore: update example module sources and versions

[wyardley]

• Update module source. This should prevent the source from getting rewritten when tests are run locally
• Add missing version spec to match other modules

Follow-up to https://github.com/terraform-google-modules/terraform-google-kubernetes-engine/pull/2115#issuecomment-2375056239

For example this:

module "permissions" {
  source = "../../modules/fleet-app-operator-permissions"
  # also no version specification here
}

gets rewritten like this when the docker test / lint make target is run.

--- a/examples/autopilot_private_firewalls/main.tf
+++ b/examples/autopilot_private_firewalls/main.tf
@@ -33,7 +33,7 @@ provider "kubernetes" {
 }

 module "gke" {
-  source                            = "../../modules/beta-autopilot-private-cluster/"
+  source                            = "wyardley/kubernetes-engine/google//modules/beta-autopilot-private-cluster"
   project_id                        = var.project_id
   name                              = "${local.cluster_type}-cluster"
   regional                          = true

[apeabody]

/gcbrun

[apeabody]

/gcbrun

[apeabody]

/gcbrun

[wyardley]

@apeabody ack, another flake maybe?

[apeabody]

@apeabody ack, another flake maybe?

Yup, slow API activation