point to new mailing list

CONTRIBUTING.md

@@ -39,10 +39,10 @@ The project uses Slack: To join the conversation, simply join the
 [#flux](https://cloud-native.slack.com/messages/flux/) channel.
 
 The Flux developers use a mailing list to discuss development as well.
-Simply subscribe to [flux-dev on Google
-Groups](https://groups.google.com/forum/#!forum/flux-dev) to join the
-conversation (this will also add an invitation to your Google calendar
-for our [Flux meeting](https://docs.google.com/document/d/1l_M0om0qUEN_NNiGgpqJ2tvsF2iioHkaARDeh6b70B0/edit#)).
+Simply subscribe to [flux-dev on cncf.io](https://lists.cncf.io/g/cncf-flux-dev)
+to join the conversation (this will also add an invitation to your
+Google calendar for our [Flux
+meeting](https://docs.google.com/document/d/1l_M0om0qUEN_NNiGgpqJ2tvsF2iioHkaARDeh6b70B0/edit#)).
 
 ## Getting Started
 

README.md

@@ -154,7 +154,7 @@ If you have any questions about Flux and continuous delivery:
   slack and ask a question on the [#flux](https://cloud-native.slack.com/messages/flux/)
   channel.
 - To be part of the conversation about Flux's development, join the
-  [flux-dev mailing list](https://groups.google.com/forum/#!forum/flux-dev).
+  [flux-dev mailing list](https://lists.cncf.io/g/cncf-flux-dev).
 - [File an issue.](https://github.com/fluxcd/flux/issues/new)
 
 Your feedback is always welcome!