Downgrade SQL Server from Enterprise to Developer edition in an Availability Group
Given that, by definition, that only happens in non-production environments, I doubt any one else has tried it.  As always, a side-by-side migration is safer than any procedure involving uninstalling and reinstalling SQL Server.
Remember, cattle, not pets.  If you have the capability to easily create a new cluster and deploy an AG on it, that procedure will satisfy a large number of operational scenarios, including this one.