Updated link to closed AngularFire discussions board

Author: tdkehoe

README.md

@@ -108,7 +108,7 @@ We have three sample apps in this repository:
 
 ### Having troubles?
 
-Get help on our [Q&A board](https://github.com/angular/angularfire/discussions?discussions_q=category%3AQ%26A), the official [Firebase Mailing List](https://groups.google.com/forum/#!forum/firebase-talk), the [Firebase Community Slack](https://firebase.community/) (`#angularfire2`), the [Angular Community Discord](http://discord.gg/angular) (`#firebase`), [Gitter](https://gitter.im/angular/angularfire2), the [Firebase subreddit](https://www.reddit.com/r/firebase), or [Stack Overflow](https://stackoverflow.com/questions/tagged/angularfire2).
+Get help on the [Firebase Community Slack](https://firebase.community/) (`#angularfire2`), the [Angular Community Discord](http://discord.gg/angular) (`#firebase`), [Gitter](https://gitter.im/angular/angularfire2), the [Firebase subreddit](https://www.reddit.com/r/firebase), or [Stack Overflow](https://stackoverflow.com/questions/tagged/angularfire2). The official [Firebase Mailing List](https://groups.google.com/forum/#!forum/firebase-talk) is closed to new discussions but you can read and comment on old discussions.
 
 > **NOTE:** AngularFire is maintained by Googlers but is not a supported Firebase product. Questions on the mailing list and issues filed here are answered on a <strong>best-effort basis</strong> by maintainers and other community members. If you are able to reproduce a problem with Firebase <em>outside of AngularFire's implementation</em>, please [file an issue on the Firebase JS SDK](https://github.com/firebase/firebase-js-sdk/issues) or reach out to the personalized [Firebase support channel](https://firebase.google.com/support/).