dbt power user previews do not work with dbt-duckdb 1.5.0

[jwills]

Reported via the DuckDB discord: if you try to execute the SQL in a dbt-duckdb 1.5.0 model in dbt power user, the process ends up holding on to the database connection in a way that prevents subsequent dbt build operations from working, viz.

Confirmed that everything works as expected here in 1.4.x, so going to try to figure out how power user is doing what it's doing and how to make it compatible with the 1.5.0 release.