docs: azure always-auth=true (#13508)

Added `always: true` to the Azure Pipeline to make sure the pipeline gets triggered on schedule even when there are no changes to the source code.

docs/usage/setup-azure-devops.md

@@ -25,6 +25,7 @@ schedules:
     displayName: 'Every day at 3am'
     branches:
       include: [main]
+    always: true
 
 trigger: none