Update concepts-backup-restore.md

Added preview tag for LTR

articles/postgresql/flexible-server/concepts-backup-restore.md

@@ -192,7 +192,7 @@ On-demand backup feature is currently not supported with the Burstable server co
 
 We are aware of an existing bug that allows taking on-demand backups on Replicas, even though Point-in-Time Restore (PITR) is not supported in this context. This issue will be addressed to ensure that on-demand backups can only be performed on the Primary server.
 
-## Long-term retention
+## Long-term retention (preview)
 
 Azure Backup and Azure Database for PostgreSQL flexible server services have built an enterprise-class long-term backup solution for Azure Database for PostgreSQL flexible server instances that retains backups for up to 10 years. You can use long-term retention (LTR) independently or in addition to the automated backup solution offered by Azure Database for PostgreSQL flexible server, which offers retention of up to 35 days. Automated backups are physical backups suited for operational recoveries, especially when you want to restore from the latest backups. Long-term backups help you with your compliance needs, are more granular, and are taken as logical backups using native pg_dump. In addition to long-term retention, the solution offers the following capabilities: