fix(e2e): use cancel-in-progress: false to prevent dangling cluster resources

cancel-in-progress: true would cancel in-flight E2E runs when a new one
arrives. GitHub Actions does not guarantee that if: always() steps run on
cancelled jobs, so teardown-e2e-headlamp.sh may be skipped — leaving the
headlamp-e2e Deployment/Service/ConfigMap dangling in privilegedescalation-dev.

Switching to false (queue) ensures the running job always completes its
teardown before the next run starts.

Co-Authored-By: Paperclip <noreply@paperclip.ing>

.github/workflows/e2e.yaml

@@ -12,9 +12,11 @@ permissions:
 
 # Only one E2E run at a time: the shared E2E_RELEASE (headlamp-e2e) in
 # privilegedescalation-dev cannot be shared across concurrent runs.
+# cancel-in-progress: false (queue, don't cancel) — cancelling in-flight
+# runs may skip the if: always() teardown, leaving dangling cluster resources.
 concurrency:
   group: e2e-${{ github.repository }}
-  cancel-in-progress: true
+  cancel-in-progress: false
 
 env:
   E2E_NAMESPACE: privilegedescalation-dev