tuf-conformance-maintainers team update

[jku]

@loosebazooka (maintainer of sigstore-java that contains a TUF implementation) volunteered to be tuf-conformance reviewer and that sounds good to me. Would be great if an org admin could invite him as member to tuf-conformance-maintainers.

[jku]

While were updating the team: @AdamKorcz, @DavidKorczynski you are of course welcome to remain as reviewers but if you don't think you'll contribute in future, I'd ask you to leave the team -- thanks for your contributions in either case.

[jku]

Nothing's happened here so I'll add appu in the project.

Note to self: if this moves forward, remove the project-specific setting