GitLab extends Omnibus package signing key expiration to 2024

The Omnibus package signing key's expiration has been extended from July 1, 2023, to July 1, 2024. This annual extension is a security policy to limit exposure if the key is compromised. The extension is preferred over rotation to minimize disruption for users who verify package integrity. Users who validate package signatures need to update their copy of the key. Instructions and URLs for obtaining the public key are provided.