The documentation is quite clear on this by stating
You can convert an SAP HANA system to support multitenant database containers. Converting an SAP HANA system to a multiple-container system is permanent and cannot be reversed.
So, no, there is no supported way "back" for the whole database.
You can however, copy the database to a system that has no other tenants. Which would give you mostly the same situation as a non MDC instance.