Updating backup service docs to clarity it is available at no cost (#59415)

Co-authored-by: mc <42146119+mchammer01@users.noreply.github.com>

Author: pallsama

content/admin/backing-up-and-restoring-your-instance/backup-service-for-github-enterprise-server/about-the-backup-service-for-github-enterprise-server.md

@@ -12,7 +12,7 @@ topics:
   - Infrastructure
 ---
 
->[!NOTE] {% data variables.product.prodname_enterprise_backup_service %} is currently in {% data variables.release-phases.public_preview %} and is subject to change. During the public preview, the service is available at no additional cost.
+>[!NOTE] {% data variables.product.prodname_enterprise_backup_service %} is currently in {% data variables.release-phases.public_preview %} and subject to change. The service is available at no additional cost and will remain free.
 
 ## About the {% data variables.product.prodname_enterprise_backup_service %}