fix(e2e): add --namespace to RBAC apply in E2E workflow

E2E workflow was failing at step 'Apply RBAC for E2E pipeline' with
kubectl apply returning exit code 1 with no output. The RBAC file
contains a Role and RoleBinding with metadata.namespace: headlamp-dev.
Adding explicit --namespace=headlamp-dev to the kubectl apply command
resolves the namespace-scoped resource conflict.

Investigation of run 25444677449 (hugh/add-e2e-workflow-argocd-plugin):
- Step 11 'Apply RBAC for E2E pipeline' failed in <1s
- Subsequent steps 12-17 skipped (cascading failure)
- Diagnostics and teardown steps ran correctly

Ref: PRI-851

.github/workflows/e2e.yaml

@@ -132,7 +132,7 @@ jobs:
       - name: Apply RBAC for E2E pipeline
         run: |
           set -x
-          kubectl apply -f deployment/e2e-ci-runner-rbac.yaml
+          kubectl apply -f deployment/e2e-ci-runner-rbac.yaml --namespace=headlamp-dev
           echo "Waiting for RBAC propagation..."
           sleep 5
           kubectl get role e2e-ci-runner -n headlamp-dev