fix: Unpin container image tag for redis and sentinel

What

Removed pinned image tag for redis and redis-sentinel containers.

Why

The image tag would come from values.yaml which is being monitored by renovate bot and version bumps are being done as expected. Renovate bot didn't update the tag, causing image tags to be pinned to a specific (older) version.

This was discovered while working locally (dev) to check for helm release updates in !832