[docs] Deleted empty code block (#19596)

## Summary & Motivation

Deleted empty code block

## How I Tested These Changes

Docs only

docs/dagster-university/pages/dagster-essentials/lesson-9/creating-an-asset-triggered-by-a-sensor.md

@@ -79,9 +79,6 @@ Now that you’ve defined how the asset can be materialized, let’s create the
      """
      ```
 
-   ```
-   ```
-
 5. Next, run the query in DuckDB and store the results as a DataFrame:
 
    ```python