bug#57306: guix pull to old commit fails due to unsupported manifest format

[Arun Isaac]

>> Commit 4ff12d1de7cd617b791996ee7ca1240660b4c20e introduced that bug,
>> which was fixed in c9fbd40785a99e13a59d8e530830ce85220a9871:

The failing commit 6f75565b4ec3b8a7247699c327a3b3196c787f76 is not in
that range, if that's what you are saying.