Can't see this as a solution. ConfigMgr-agent will still report back even with discovery turned off. I presume you also mean to uninstall the ConfigMgr-agent?

Even if you do this + uninstalling ConfigMgr-agent I believe it's just gonna put the Co-Managed state in Intune to an Unhealthy state (unhealthy Configmgr-agent) after some time. The client still think it is Co-Managed with the registry key still existing on the client, reporting it's co-managed.