remove regional high availability

tidb-cloud/tidb-cloud-release-notes.md

@@ -14,18 +14,6 @@ This page lists the release notes of [TiDB Cloud](https://www.pingcap.com/tidb-c
 
 - Upgrade the default TiDB version of new [TiDB Cloud Dedicated](/tidb-cloud/select-cluster-tier.md#tidb-cloud-dedicated) clusters from [v7.5.4](https://docs.pingcap.com/tidb/v7.5/release-7.5.4) to [v8.1.1](https://docs.pingcap.com/tidb/stable/release-8.1.1).
 
-- Regional high availability (beta) for [TiDB Cloud Serverless](/tidb-cloud/select-cluster-tier.md#tidb-cloud-serverless) clusters.
-
-    This feature is designed for workloads that require maximum infrastructure redundancy and business continuity. Key features include:
-
-    - Nodes are distributed across multiple availability zones to ensure high availability in the event of a zone failure.
-    - Critical OLTP (Online Transactional Processing) components, such as PD and TiKV, are replicated across availability zones for redundancy.
-    - Automatic failover minimizes service disruption during a primary zone failure.
-
-  This feature is currently available only in the AWS Tokyo (`ap-northeast-1`) region and can be enabled only during cluster creation.
-
-    For more information, see [High Availability in TiDB Cloud Serverless](/tidb-cloud/serverless-high-availability.md).
-
 - [TiDB Cloud Serverless](/tidb-cloud/select-cluster-tier.md#tidb-cloud-serverless) reduces costs for large data writes by up to 80% for the following scenarios:
 
     - When you perform write operations larger than 16 MiB in [autocommit mode](/transaction-overview.md#autocommit).