[du] fixing imports for 4-automating-dbt-models-in-dagster (#21765)

## Summary & Motivation

## How I Tested These Changes

docs/dagster-university/pages/dagster-dbt/lesson-5/4-automating-dbt-models-in-dagster.md

@@ -39,10 +39,11 @@ This is where you’d lean on a function like [`build_dbt_asset_selection`](http
 
 The function will return an `AssetSelection` of the dbt models that match your dbt selector. Let’s put this into practice:
 
-1. At the top of `jobs/__init__.py`, import `dbt_analytics` from the `assets.dbt` module:
+1. At the top of `jobs/__init__.py`, import `dbt_analytics` from the `assets.dbt` module, along with the `build_dbt_asset_selection` function from `dagster_dbt`:
 
     ```python
     from ..assets.dbt import dbt_analytics
+    from dagster_dbt import build_dbt_asset_selection
     ```
 
 2. After the other selections, define a new variable called `dbt_trips_selection` and make a call to `build_dbt_asset_selection`. Pass in the `dbt_analytics` definition and a string that selects `stg_trips` and all dbt models downstream of it: