chore(repo): update old heroku app links (#27284)

Issue number: N/A

---------

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## What is the current behavior?
<!-- Please describe the current behavior that you are modifying. -->

there are a few outdated links to a dead heroku app in the repo

## What is the new behavior?

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this PR. -->
this commit removes old links within the repo that point to a heroku app
that is no longer working/maintained. the original intent was to update
stencil-related links initially (as stencil still focuses on slack for
community communications). however, there were two references to the
ionic worldwide slack, which has been since replaced with discord. i've
updated those link (which were only in comments) as well. after applying
this commit, there are no references to 'heroku' in the repo

## Does this introduce a breaking change?

- [ ] Yes
- [x] No

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and migration path for existing applications below. -->


## Other information

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screenshots of how the component looks before and after the change. -->

Feel free to reject this/request we remove these links altogether. I'm
not entirely sure we want to continue to provide them in the `core/` and
`angular/` directories (when we don't have them in `packages/react/` nor
`packages/vue/`

.github/ISSUE_TEMPLATE.md

@@ -2,7 +2,7 @@
 
 <!-- Please make sure you are posting an issue pertaining to the Ionic Framework. If you are having an issue with the Ionic Appflow services (Ionic View, Ionic Deploy, etc.) please consult the Ionic Appflow support portal (https://ionic.zendesk.com/hc/en-us) -->
 
-<!-- Please do not submit support requests or "How to" questions here. Instead, please use one of these channels: https://forum.ionicframework.com/ or http://ionicworldwide.herokuapp.com/ -->
+<!-- Please do not submit support requests or "How to" questions here. Instead, please use one of these channels: https://forum.ionicframework.com/ or https://ionic.link/discord/ -->
 
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@@ -17,7 +17,7 @@
 [ ] bug report
 [ ] feature request
 
-<!-- Please do not submit support requests or "How to" questions here. Instead, please use one of these channels: https://forum.ionicframework.com/ or http://ionicworldwide.herokuapp.com/ -->
+<!-- Please do not submit support requests or "How to" questions here. Instead, please use one of these channels: https://forum.ionicframework.com/ or https://ionic.link/discord -->
 
 **Current behavior:**
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angular/README.md

@@ -10,7 +10,7 @@ Ionic Angular specific building blocks on top of [@ionic/core](https://www.npmjs
 * [Ionic Forum](https://forum.ionicframework.com/)
 * [Ionicons](http://ionicons.com/)
 * [Stencil](https://stenciljs.com/)
-* [Stencil Worldwide Slack](https://stencil-worldwide.herokuapp.com/)
+* [Stencil Worldwide Slack](https://stencil-worldwide.slack.com/)
 * [Capacitor](https://capacitor.ionicframework.com/)
 
 

core/README.md

@@ -104,7 +104,7 @@ const showModal = async () => {
 * [Ionic Forum](https://forum.ionicframework.com/)
 * [Ionicons](http://ionicons.com/)
 * [Stencil](https://stenciljs.com/)
-* [Stencil Worldwide Slack](https://stencil-worldwide.herokuapp.com/)
+* [Stencil Worldwide Slack](https://stencil-worldwide.slack.com/)
 * [Capacitor](https://capacitor.ionicframework.com/)