Update Grafana chart version to 6.9.0

Summary

This relates to #2698 (closed)

The current grafana chart 4.0.1 has the deprecated API rbac.authorization.k8s.io/v1beta1 which should also be migrated to rbac.authorization.k8s.io/v1 as support ends from v1.22+

# Source: gitlab/charts/grafana/templates/role.yaml
apiVersion: rbac.authorization.k8s.io/v1beta1
kind: Role
metadata:
  name: gitlab-grafana
  namespace: gitlab

Current behavior

The generated Roles and Rolebindings reference the deprecated API rbac.authorization.k8s.io/v1beta1

Expected behavior

This should be migrated to rbac.authorization.k8s.io/v1

Versions

• Chart: 4.11.3