Delete the non-ASF release

Author: tuhaihe

docs/releases/index.md

@@ -1,7 +1,8 @@
 # Releases
 
-```mdx-code-block
-import DocCardList from '@theme/DocCardList';
+**Note:**
 
-<DocCardList />
-```
+We are currently preparing for the release under the Apache Incubator. Previous versions were non-Apache releases. If you want to install Apache Cloudberry, you can either:
+
+* **Manually build Cloudberry from the main branch**: This approach is suitable for developers or users who want to experience the latest features. You can clone the repository and follow the build instructions provided in the documentation.
+* **Install the non-Apache release: [v1.6.0](https://github.com/apache/cloudberry/releases/tag/1.6.0)**: This version is stable and ready for production use, offering the rpm packages for both Enterprise Linux 8 and 9 version.