CONTRIBUTING.md in thinreports-0.12.0

- old
+ new

@@ -1,2 +1,2 @@
-**We only accept bug reports and pull requests in GitHub**.
-If you have a support question about how to use thinreports, please [ask on Google Group](https://groups.google.com/forum/?hl=ja#!forum/thinreports).
+We only accept bug reports and pull requests in GitHub.
+If you have a support question about how to use thinreports, please [ask on GitHub Discussions](https://github.com/thinreports/thinreports/discussions).