Update release-8.5.0.md

Add GCP KMS content

releases/release-8.5.0.md

@@ -123,6 +123,13 @@ Compared with the previous LTS 8.1.0, 8.5.0 includes new features, improvements,
 
   For more information, see [documentation](/br/br-pitr-manual.md#encrypt-the-log-backup-data).
 
+* TiKV encryption at rest supports Google [Key Management Service (Cloud KMS)](https://cloud.google.com/docs/security/key-management-deep-dive?hl) (GA) [#8906](https://github.com/tikv/tikv/issues/8906) @[glorv](https://github.com/glorv)
+
+    In v8.0.0, TiKV has supported this feature as an experimental feature. TiKV supports configuring Google Cloud KMS-based master keys for encryption at rest. Starting from v8.5.0, this feature is now Generally Avaialble.
+    To enable encryption at rest based on Google Cloud KMS, you need to create a key on Google Cloud and then configure the `[security.encryption.master-key]` section in the TiKV configuration file.
+
+    For more information, see [documentation](/encryption-at-rest.md#tikv-encryption-at-rest).
+
 ### Data migration
 
 * Placeholder for feature summary [#Issue-number](issue-link) @[Contributor-GitHub-ID](id-link) **tw@xxx** <!--1234-->