We used to release the message-relayer package externally to distribute various utilities related to relaying messages. All of this functionality has now been moved into @eth-optimism/sdk. Since we have no need to continue publishing this package on NPM, we should mark the package as private by modifying its package.json file.

All we need to do is to add "private": "true" to the top of the file. You can see an example here within replica-healthcheck: