Fix wrong indent in notebook overview

Signed-off-by: Patrick Bloebaum <[email protected]>

Author: bloebp

docs/source/example_notebooks/nb_index.rst

@@ -198,7 +198,7 @@ Real world-inspired examples
         | **Level:** Advanced
         | **Task:** Fairness estimation via GCM
 
-   .. grid-item-card:: :doc:`sales_attribution_intervention`
+    .. grid-item-card:: :doc:`sales_attribution_intervention`
 
         .. image:: ../_static/sales_attribution.png
             :height: 120px