deleteBlob method
      
  
Future<List<BlobDeleteResult> > 
deleteBlob({ 
    
- required String sha256,
- required List<String> serverUrls,
- required Nip01Event authorization,
override
    Attempts to delete blob from all servers
Implementation
@override
Future<List<BlobDeleteResult>> deleteBlob({
  required String sha256,
  required List<String> serverUrls,
  required Nip01Event authorization,
}) async {
  final results = await Future.wait(serverUrls.map((url) => _deleteFromServer(
        serverUrl: url,
        sha256: sha256,
        authorization: authorization,
      )));
  return results;
}