message: use slack's invite portal
diff: @@ -4,7 +4,7 @@ gnina is **not** recommended for production use (*yet*) in molecular modeling ta
  Help
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  -**Reminder: gnina is not yet intended for production use**. However, if you would like to evaluate it or use it as a research platform, please [subscribe to our slack team](http://bits.csb.pitt.edu/slack).
  +**Reminder: gnina is not yet intended for production use**. However, if you would like to evaluate it or use it as a research platform, please [subscribe to our slack team](https://join.slack.com/t/gninacnn/shared_invite/enQtNTY3ODk2ODk5OTU5LWUxNzIzOTc3OWJiOTY3N2ZhYzgzY2IzZTBiYjMyZGVjY2UyNDlhZDkyYjk5OTY2M2M2ZGEzZjNkMjhlNGQ0NGE).
  Citation
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