gatekeeper update to 3.21.0-bb.1

Package Merge Request

Package Changes

https://repo1.dso.mil/big-bang/product/packages/policy/-/blob/3.21.0-bb.1/CHANGELOG.md

Package MR

big-bang/product/packages/policy!329 (merged)

For Issue

Closes big-bang/product/packages/policy#290 (closed)

Upgrade Notices

Breaking changes

Gatekeeper has moved to passthrough and certain values will need to be migrated under the upstream label. For example

gatekeeper:
  # -- Toggle deployment of OPA Gatekeeper.
  enabled: false

  # -- Values to passthrough to the gatekeeper chart: https://repo1.dso.mil/big-bang/product/packages/policy.git
  values: 
    upstream:
      replicas: 1

These upstream value are defined here: https://github.com/open-policy-agent/gatekeeper/blob/master/charts/gatekeeper/values.yaml