Remove reference to Google groups in README (#2838)

Changing it with a link to the forums.

Author: PetyaSotirova

README.md

@@ -377,7 +377,7 @@ tns doctor
 
 This command prints warnings about current configuration issues and provides basic information about how to resolve them.
 
-If addressing the configuration issues does not resolve your problem, you can [report an issue](https://github.com/NativeScript/nativescript-cli/blob/master/CONTRIBUTING.md#report-an-issue) or [post in the NativeScript page in Google Groups](https://groups.google.com/forum/#!forum/nativescript).
+If addressing the configuration issues does not resolve your problem, you can [report an issue](https://github.com/NativeScript/nativescript-cli/blob/master/CONTRIBUTING.md#report-an-issue) or [post in the NativeScript forums](https://discourse.nativescript.org/).
 
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