The managed resource group cannot be the same as the rg-france-prod parent resource group.
The nested structure is as follows: parent resource group > managed application > managed resource group.
The Managed Resource Group is created during deployment and will contain all resources deployed as part of the deployment (VM, Public IP, NIC, DIsk etc)
This structure allows the Managed Application Publisher (Cisco Meraki) to have Admin-level access to resources in the Managed Resource Group to maintain/control aspects of the deployment on an ongoing basis (this Co-Admin permission is presented on the Review + Create tab during your deployment)
TL;DR specify a different, unique value in this box, i.e mrg-france-prod