changelog: note s3 operator flag deprecation
- Add cluster S3 spec `prefix` feature. Let user choose a prefix under the bucket.
- Add `automountServiceAccountToken` to pod policy. Let users disable automounting of the Kubernetes access token into etcd-operator controlled pods.
- Cluster backups can now be saved using Azure Blob Storage (ABS).
+- Add warning/note on deprecating s3 operator flag.
### Changed
