release.hs: use SHA256 digests for GPG signatures
release.hs: use SHA256 digests for GPG signatures

(#1934)

AndreasPK/stack,Heather/stack,anton-dessiatov/stack,deech/stack,phadej/stack,Heather/stack,MichielDerhaeg/stack,phadej/stack,mrkkrp/stack,mrkkrp/stack,narrative/stack,juhp/stack,AndreasPK/stack,AndrewRademacher/stack,deech/stack,martin-kolinek/stack,juhp/stack,sjakobi/stack,Fuuzetsu/stack,MichielDerhaeg/stack,anton-dessiatov/stack,narrative/stack,Fuuzetsu/stack,martin-kolinek/stack,Blaisorblade/stack,sjakobi/stack,AndrewRademacher/stack,Blaisorblade/stack