docs: remove trailing blank line in cockpit migration guide

Author: jremy42

docs/guides/migration_guide_cockpit_alert_manager.md

@@ -163,4 +163,3 @@ If Terraform shows unexpected changes to `preconfigured_alert_ids`:
 - [Cockpit Alert Manager Resource Documentation](../resources/cockpit_alert_manager.md)
 - [Cockpit Preconfigured Alert Data Source Documentation](../data-sources/cockpit_preconfigured_alert.md)
 - [Scaleway Cockpit Documentation](https://www.scaleway.com/en/docs/observability/cockpit/)
-