The slack link is already dead

### Search before asking

- [X] I had searched in the [issues](https://github.com/apache/eventmesh/issues?q=is%3Aissue) and found no similar issues.


### Environment

Chrome

### What happened

join slack button is broken

### How to reproduce

click the join slack button

### Debug logs

_No response_

### Are you willing to submit PR?

- [x] Yes I am willing to submit a PR!