update slack link

(cherry picked from commit af6ece8)

Author: oilbeater

mkdocs.yml

@@ -191,7 +191,7 @@ extra:
     - icon: fontawesome/brands/weixin
       link: http://page.alauda.cn/kubeovn
     - icon: fontawesome/brands/slack
-      link: https://kube-ovn-slackin.herokuapp.com/
+      link: https://communityinviter.com/apps/kube-ovn/kube-ovn/
     - icon: fontawesome/brands/twitter
       link: https://twitter.com/kubeovn
     - icon: fontawesome/brands/github

overrides/contact.md

@@ -1,4 +1,4 @@
 [:material-wechat: 微信群](https://ma.alauda.cn/p/0f39a){: target="_blank" .md-button }
-[:material-slack: Slack](https://kube-ovn-slackin.herokuapp.com/){: target="_blank" .md-button }
+[:material-slack: Slack](https://communityinviter.com/apps/kube-ovn/kube-ovn/){: target="_blank" .md-button }
 [:material-twitter: Twitter](https://twitter.com/KubeOvn){: target="_blank" .md-button }
 [:material-email: Support](https://ma.alauda.cn/p/2f53a){: target="_blank" .md-button }