lib/json{,_fwd}.hpp: upgrade to 3.9.1
Such an upgraded library is needed to compile on some non-standard systems.
[En cours] Mise en place de quotas sur nos instances GitLab. Plus d'information sur : https://doc-si.inria.fr/pages/viewpage.action?pageId=146834656
[In progress] Quotas installation on our GitLab instances. More information: https://doc-si.inria.fr/pages/viewpage.action?pageId=146834656
Such an upgraded library is needed to compile on some non-standard systems.