fix(auth): do auth dance even when basic auth creds are not found

[whatsacomputertho]

In this PR, I remove the found condition from the if statement around the auth dances performed to fetch a token from the registry auth server. This condition required that the user provide basic auth creds in their initial request only for those creds to then fail on the initial request, with a 401 response sent back and a www-authenticate header instructing the client to fetch a token from the auth server. Some registries (such as ghcr.io) require this dance for all clients regardless of whether the image is public or private. Removing this condition seems to work now for public ghcr.io images.

For reference, see:

• Fails to pull a public image from: ghcr.io/matejvasek/builder-ubi8-base:latest #30