In https://gitlab.com/gitlab-org/gitlab/merge_requests/23754 and
https://gitlab.com/gitlab-org/gitlab/-/merge_requests/24408, we
added a CTE optimization fence to ensure loading a user's projects is
always fast when the `/dashboard/projects` path is loaded.

However, when sorting by a different column type (e.g. last created),
PostgreSQL would raise an ambiguous column error because it wasn't clear
which `created_at` column was needed.

To fix this problem, we should be explicit that we want to order by
`projects.created_at`.

Foo