Deletes an existing backup of a table.Show details from next link. https://docs.aws.amazon.com/ja_jp/cli/latest/reference/dynamodb/delete-backup.html
| aws dynamodb delete-backup \ |
| Deleting a DynamoDB Table Backup - Amazon DynamoDB : http://docs.aws.amazon.com/amazondynamodb/latest/developerguide/Delete.Tutorial.html |