Keep previews' AWS creds up to date

After 7 days, the running previews are broken.

See improvement https://github.com/nuxeo/nuxeo-ai-integration/commit/9f6dc6e?branch=9f6dc6ed231975821046f23d35749c59389c5278&diff=unified

 The AWS creds are rotated while they're in use by the previews. Instead of using an immutable configmap, using a replicated k8s secret key mounted on the pod will trigger a pod restart with updated credentials.