Correct group by in daily_metrics model

docs/dagster-university/pages/dagster-dbt/lesson-6/2-creating-a-simple-incremental-model.md

@@ -36,7 +36,7 @@ with
             sum(total_amount) / count(*) as average_amount,
             sum(case when duration > 30 then 1 else 0 end) / count(*) as pct_over_30_min
         from trips
-        group by all
+        group by date_of_business
     )
 select *
 from daily_summary