Merge pull request #2522 from RainbowMango/pr_update_slack

Update slack address in badge

README.md

@@ -7,7 +7,7 @@
 [![Go Report Card](https://goreportcard.com/badge/github.com/karmada-io/karmada)](https://goreportcard.com/report/github.com/karmada-io/karmada)
 [![LICENSE](https://img.shields.io/github/license/karmada-io/karmada.svg)](/LICENSE)
 [![Releases](https://img.shields.io/github/release/karmada-io/karmada/all.svg)](https://github.com/karmada-io/karmada/releases)
-[![Slack](https://img.shields.io/badge/slack-join-brightgreen)](https://join.slack.com/t/karmada-io/shared_invite/zt-omhy1wfa-LmAkCLfpDMnBjVXp3_U~0w)
+[![Slack](https://img.shields.io/badge/slack-join-brightgreen)](https://slack.cncf.io)
 [![CII Best Practices](https://bestpractices.coreinfrastructure.org/projects/5301/badge)](https://bestpractices.coreinfrastructure.org/projects/5301)
 
 ## Karmada: Open, Multi-Cloud, Multi-Cluster Kubernetes Orchestration