Use BigBang Redis for Gitlab

Current Gitlab chart uses internal Redis Chart

• Switch to Big Bang Redis
• Reference Argo MR
  • kpt the 12.8.3-bb.0 tag for redis into chart/external
  • change the dependency to reference the external folder. Alias may not be needed.

- name: redis
  version: 12.8.3-bb.0
  repository: file://external
  condition: redis-ha.enabled
  alias: redis-bb

• Run helm dep update chart from the top level
• Redis has imagepullsecrets configured for private-registry by default, so no configuration should be needed there.