Deprecate the machine license validation scope

Nobody really uses the `meta.scope.machine` scope, and it's confusing as-is. We could combine it with `meta.scope.fingerprint` to accept an ID or fingerprint, like the `meta.scope.user` scope does with email and ID, making `meta.scope.fingerprint` and `meta.scope.machine` synonymous. We can remove docs for one to push people towards the other.