[PostgreSQL] remove preview

Author: markingmyname

articles/postgresql/migrate/migration-service/concepts-migration-service-postgresql.md

@@ -10,7 +10,7 @@ ms.subservice: flexible-server
 ms.topic: conceptual
 ---
 
-# Migration service in Azure Database for PostgreSQL Preview
+# Migration service in Azure Database for PostgreSQL
 
 [!INCLUDE [applies-to-postgresql-flexible-server](../../includes/applies-to-postgresql-flexible-server.md)]