Fix release badge (#13206)

We don't release to maven central, so change the release badge attaching on the GH release.

Author: wu-sheng

README.md

@@ -9,7 +9,7 @@ microservices, cloud native and container-based architectures.
 [![GitHub stars](https://img.shields.io/github/stars/apache/skywalking.svg?style=for-the-badge&label=Stars&logo=github)](https://github.com/apache/skywalking)
 [![X Follow](https://img.shields.io/badge/2K%2B-follow?style=for-the-badge&logo=X&label=%40ASFSKYWALKING)](https://x.com/AsfSkyWalking)
 
-[![Maven Central](https://img.shields.io/maven-central/v/org.apache.skywalking/apache-skywalking-apm.svg)](http://skywalking.apache.org/downloads/)
+![GitHub Release](https://img.shields.io/github/v/release/apache/skywalking)
 
 # Abstract
 **SkyWalking** is an open-source APM system that provides monitoring, tracing and diagnosing capabilities for distributed systems in Cloud Native architectures.