Update april-2024.md

Author: xboxeer

articles/mysql/flexible-server/release-notes/april-2024.md

@@ -19,10 +19,10 @@ All existing engine version server upgrades to 8.0.36 engine version.
 To check your engine version, run `SELECT VERSION();` command at the MySQL prompt
 
 ## Features
-- Support for LTR backups for Azure DB for MySQL Flexible Server
 - Support for Azure Defender for Azure DB for MySQL Flexible Server
 
 ## Improvement
+- [Support for Long-term retention of backups in Azure Database for MySQL Flexible Server (Preview)](../concepts-backup-restore.md#long-term-retention-preview)
 - Expose old_alter_table for 8.0.x.
 
 ## Known Issues Fix