Remove synergized device

I have an old Transit Duo as a synergized device on the WAN port of a MAX BR1 Pro 5G HW1. The Transit Duo is powered off at this point, and I plan to remove it entirely and go a different route for this installation (maybe a BR2 Pro 5G, or a Transit Duo Pro). How do I get the Max BR1 Pro 5G to forget about the Transit Duo?

The MAX BR1 Pro 5G is on 8.4.0.