Update Guix command in .gitlab-ci.yml
Works on my machine, check if the CI still works once merged.
Prochaines maintenances programmées: lundi 06/05, lundi 03/06, lundi 01/07
Pour plus d'informations: https://doc-si.inria.fr/display/SU/Gitlab
Works on my machine, check if the CI still works once merged.