bug#59830: guix system reconfigure don't work after 1.4_rc1 fresh installation

[Christophe Pisteur]

## Step to reproduce

Fresh intallation with guix-system-install-1.4.0rc1.x86_64-linux.iso

guix pull

guix package -u

sudo guix system reconfigure /etc/config.scm

## Expected result

the system is upgraded

** Unexpected result

guix system: erreur : aborting reconfiguration because commit d7c8cb7e53682a52a80bd35e2deaaab7f3e0c912 of channel 'guix' is not a descendant of 883fefe1605499c8d98426f2915816dddd7448ef

conseil : Utilisez `--allow-downgrades' pour forcer ce retour en arrière.

## Note:

I did the installation twice with the same result, once with guix package -u once without guix package -u before guix system reconfigure

Hardware:

Lenovo T400 with libreboot

Intel core T9900 × 2

sda /

sdb /home (encrypted)