Deprovisioning a Chrome device removes it from management. It is intended for devices that are no longer active, that are being resold, or that are being submitted for return / repair. Once a device is deprovisioned, the device must also be wiped before it can be re-enrolled. Re-enrollment is a manual only process (e.g. deprovisioning cannot be un-done via Chrome Gopher) so be careful!!
From the Bulk actions tab of the Chrome Gopher sidebar, select Deprovision
A stepper will guide you through the process of deprovisioning the devices.