tests: upgrade GKE test cluster to v1.32 (#3504)

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### Proposed changes

GKE has dropped support for v1.28 clusters, causing CI to fail when
creating a test cluster. This PR upgrades our test clusters to use GKE
v1.32.

### Related issues (optional)

Closes: #3503

tests/ci-cluster/gke.ts

@@ -26,8 +26,8 @@ export class GkeCluster extends pulumi.ComponentResource {
                 opts: pulumi.ComponentResourceOptions = {}) {
         super("pulumi-kubernetes:ci:GkeCluster", name, {}, opts);
 
-        // Use the latest 1.28.x engine version.
-        const engineVersion = "1.28";
+        // Use the latest 1.32.x engine version.
+        const engineVersion = "1.32";
 
         // Create the GKE cluster.
         const k8sCluster = new gcp.container.Cluster("ephemeral-ci-cluster", {