Distribution: Tag deletion bypasses `storage.delete.enabled` configuration

Distribution is a toolkit to pack, ship, store, and deliver container content. Prior to 3.1.1, tag deletion via the DELETE /v2/<name>/manifests/<tag> endpoint bypasses the storage.delete.enabled: false configuration, allowing any API client to remove tags from repositories even when the operator has explicitly disabled deletion. This vulnerability is fixed in 3.1.1.