Removes an image from the tenant's library, releasing any pin it held and stripping every link to it. Requires an Enterprise subscription and the brand image library enabled for the tenant. Identifiers that were linked to it are left untouched; a domain identifier with no images left goes back to being crawled live. The delete is idempotent: an imageID that is not in the library succeeds rather than returning 404, because a library read that fails cannot be told apart from one that finds nothing, and answering "no such image" for a transient error would be a lie. Call list-brand-images to learn what is actually there.