fix(benefits): add group_properties column to external table (#2599)

Author: machikoyasuda

airflow/dags/create_external_tables/amplitude/benefits_events.yml

@@ -60,6 +60,8 @@ schema_fields:
     type: STRING
   - name: dma
     type: STRING
+  - name: group_properties
+    type: JSON
   - name: event_properties
     type: JSON
   - name: user_properties