Update exporting-directory-level-activity-logs-to-event-hub.md

Minor update to add H2 heading to Reference section.

Author: Amson Liu

support/azure/azure-monitor/activity-logs/config-export/exporting-directory-level-activity-logs-to-event-hub.md

@@ -44,7 +44,7 @@ Exporting directory-level activity logs to an Event Hub can be achieved through
 - **Issue:** Permission errors when setting up diagnostic settings.
   - **Solution:** Ensure you have the necessary permissions to create or update diagnostic settings in Azure.
 
-Reference
+## Reference
 
 - [Azure Monitor Documentation](https://learn.microsoft.com/azure/monitoring/)
 - [Event Hubs Documentation](https://learn.microsoft.com/azure/event-hubs/)