ci(helm): fix rollout wait to target StatefulSet, not Deployment

The agent-sandbox controller manifest installs a StatefulSet, not a
Deployment, so kubectl rollout status was 404'ing on the wrong kind.

Signed-off-by: Taylor Mutch <taylormutch@gmail.com>

Author: TaylorMutch

.github/workflows/branch-helm-e2e.yml

@@ -127,7 +127,7 @@ jobs:
           set -euo pipefail
           kubectl --kubeconfig "$GITHUB_WORKSPACE/kubeconfig" apply -f deploy/kube/manifests/agent-sandbox.yaml
           kubectl --kubeconfig "$GITHUB_WORKSPACE/kubeconfig" wait --for=condition=Established crd/sandboxes.agents.x-k8s.io --timeout=120s
-          kubectl --kubeconfig "$GITHUB_WORKSPACE/kubeconfig" -n agent-sandbox-system rollout status deployment/agent-sandbox-controller --timeout=300s
+          kubectl --kubeconfig "$GITHUB_WORKSPACE/kubeconfig" -n agent-sandbox-system rollout status statefulset/agent-sandbox-controller --timeout=300s
 
       - name: Run Helm E2E (Rust smoke)
         env: