docs: fix mailing list URL
@@ -65,7 +65,7 @@ For more information in the source, here are some pointers:
Developers welcome!
-* [Our developer mailing list](http://lists.runtime.co/mailman/listinfo/dev-mcuboot_lists.runtime.co)
+* [Our developer mailing list](https://groups.io/g/MCUBoot)
* [Our Slack channel](https://mcuboot.slack.com/)<br />
Get your invite [here!](https://join.slack.com/t/mcuboot/shared_invite/MjE2NDcwMTQ2MTYyLTE1MDA4MTIzNTAtYzgyZTU0NjFkMg)
* [Our IRC channel](http://irc.freenode.net), channel #mcuboot ([IRC
