log_reuse_wait_desc says ACTIVE TRANSACTION but DBCC OPENTRAN reports nothing
Because this is AdventureWorks and obviously not a production server, you're probably not going to get great answers here. I'd just restart the server. (Is that the right answer? No, but we're obviously talking about a development playground box here, and I wanna get you across the finish line quickly.)

If you really wanted to troubleshoot it, try sp_WhoIsActive:

sp_WhoIsActive @show_sleeping_spids = 1, @show_system_spids = 1, @show_own_spid = 1


Just because if you're getting started with transaction troubleshooting, I'd rather give you something easier to use than DBCC commands.