Wrong mediatype on attestation replace

[stgrace]

Description

Using replace option on cosing attest, an attestation with wrong mediatype is created, namely mediaType application/vnd.docker.distribution.manifest.v2+json instead of application/vnd.oci.image.manifest.v1+json. This results in tool like skopeo throwing an error:

FATA[0001] Error parsing manifest for image: unsupported docker v2s2 media type: "application/vnd.oci.image.manifest.v1+json"

Version

Latest and greatest