Fixes#15302

The subquery on the users table was incorrectly using the username from theworkspaces table, not theusers table.

This passedsqlc-vet because the column did exist in the query, it just was not the correct one.

Note: If we do not care aboutdeleted users, we can drop querying theUsers table at all and use theowner_username on the workspaces. But then we'd get deleted users with the same name 😢