Remove useless file (#9258)

roles/kubernetes-apps/ingress_controller/ingress_nginx/templates/role-admission-webhook.ym.j2

----
-apiVersion: rbac.authorization.k8s.io/v1
-kind: Role
-metadata:
-  labels:
-    app.kubernetes.io/name: ingress-nginx
-    app.kubernetes.io/part-of: ingress-nginx
-  name: ingress-nginx-admission
-  namespace: {{ ingress_nginx_namespace }}
-rules:
-- apiGroups:
-  - ""
-  resources:
-  - secrets
-  verbs:
-  - get
-  - create