fix(e2e): reference shared infra RBAC instead of local file (PRI-720)

Remove deployment/e2e-ci-runner-rbac.yaml — RBAC is now managed via
Flux GitOps from privilegedescalation/infra/base/rbac/e2e-ci-runner-headlamp-rbac.yaml.

Changes:
- .github/workflows/e2e.yaml: Remove local RBAC apply steps (no longer
  applying local file); RBAC pre-flight check now verifies all required
  roles/rolebindings are present (managed elsewhere via Flux)
- scripts/deploy-e2e-headlamp.sh: Update error message to point to the
  infra repo raw URL instead of the removed local file

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

deployment/e2e-ci-runner-rbac.yaml

@@ -1,74 +0,0 @@
----
-# RBAC for the GitHub Actions CI runner to manage the E2E Headlamp instance.
-# CI-only test fixture — NOT for production use.
-#
-# Grants the ARC runner service account permissions in the headlamp-dev
-# namespace to deploy and tear down a dedicated Headlamp instance via Helm.
-# E2E resources run in `headlamp-dev` — nothing persists beyond a test run.
-#
-# Plugin is loaded via ConfigMap volume mount — no custom Docker images.
-#
-# Note: This RBAC is mirrored in privilegedescalation/infra (base/rbac/)
-# and managed by Flux GitOps. The infra repo is the source of truth.
-apiVersion: rbac.authorization.k8s.io/v1
-kind: Role
-metadata:
-  name: e2e-ci-runner
-  namespace: headlamp-dev
-rules:
-  # Helm needs to manage these resources for the Headlamp chart
-  - apiGroups: ["apps"]
-    resources: ["deployments"]
-    verbs: ["get", "list", "create", "update", "patch", "delete", "watch"]
-  - apiGroups: [""]
-    resources: ["services", "serviceaccounts", "configmaps", "secrets", "events"]
-    verbs: ["get", "list", "watch", "create", "update", "patch", "delete"]
-  - apiGroups: [""]
-    resources: ["pods"]
-    verbs: ["get", "list", "watch"]
-  # Token creation for E2E test auth
-  - apiGroups: [""]
-    resources: ["serviceaccounts/token"]
-    verbs: ["create"]
-  # Apply Polaris dashboard RBAC in the polaris namespace
-  - apiGroups: ["rbac.authorization.k8s.io"]
-    resources: ["roles", "rolebindings"]
-    verbs: ["get", "list", "create", "update", "patch", "delete"]
----
-apiVersion: rbac.authorization.k8s.io/v1
-kind: Role
-metadata:
-  name: e2e-ci-runner-polaris
-  namespace: polaris
-rules:
-  - apiGroups: ["rbac.authorization.k8s.io"]
-    resources: ["roles", "rolebindings"]
-    verbs: ["get", "list", "create", "update", "patch", "delete"]
----
-apiVersion: rbac.authorization.k8s.io/v1
-kind: RoleBinding
-metadata:
-  name: e2e-ci-runner-polaris
-  namespace: polaris
-subjects:
-  - kind: ServiceAccount
-    name: runners-privilegedescalation-gha-rs-no-permission
-    namespace: arc-runners
-roleRef:
-  kind: Role
-  name: e2e-ci-runner-polaris
-  apiGroup: rbac.authorization.k8s.io
----
-apiVersion: rbac.authorization.k8s.io/v1
-kind: RoleBinding
-metadata:
-  name: e2e-ci-runner-binding
-  namespace: headlamp-dev
-subjects:
-  - kind: ServiceAccount
-    name: runners-privilegedescalation-gha-rs-no-permission
-    namespace: arc-runners
-roleRef:
-  kind: Role
-  name: e2e-ci-runner
-  apiGroup: rbac.authorization.k8s.io