[ResponseOps][MaintenanceWindow][9.1 & Serverless] Add delete MW operation to UI (elastic#2703)

Contributes to elastic#2455 by
adding that Maintenance Windows can be deleted in 9.1+.

**Corresponding 8.19 PR**: elastic/kibana#232841

Preview -
https://docs-v3-preview.elastic.dev/elastic/docs-content/pull/2703/explore-analyze/alerts-cases/alerts/maintenance-windows#manage-maintenance-windows

Author: nastasha-solomon

explore-analyze/alerts-cases/alerts/maintenance-windows.md

@@ -39,7 +39,9 @@ For more details, refer to [{{kib}} privileges](../../../deploy-manage/users-rol
 
 ## Create and manange maintenance windows [manage-maintenance-windows]
 
-In **Management > {{stack-manage-app}} > Maintenance Windows** or **{{project-settings}} > {{manage-app}} > {{maint-windows-app}}** in Serverless, you can create, edit, and archive maintenance windows.
+In **Management > {{stack-manage-app}} > Maintenance Windows** or **{{project-settings}} > {{manage-app}} > {{maint-windows-app}}** in Serverless, you can create, edit, cancel, and archive maintenance windows. 
+
+{applies_to}`stack: ga 9.1` In {{stack}} 9.1.0 and later, you can also delete maintenance windows that are running, canceled, or archived. Be aware that you can't recover maintenance windows once you delete them.
 
 When you create a maintenance window, you must provide a name and a schedule. You can optionally configure it to repeat daily, monthly, yearly, or on a custom interval.