chore(ionitron): remove reference to old Slack channel (#24189)

Author: averyjohnston

.github/ionic-issue-bot.yml

@@ -41,8 +41,7 @@ closeAndLock:
     - label: "ionitron: support"
       message: >
         Thanks for the issue! This issue appears to be a support request. We use this issue tracker exclusively for
-        bug reports and feature requests. Please use our [forum](https://forum.ionicframework.com) or our
-        [slack channel](https://ionicworldwide.herokuapp.com/) for questions about the framework.
+        bug reports and feature requests. Please use our [forum](https://forum.ionicframework.com) for questions about the framework.
 
 
         Thank you for using Ionic!