Update mailing list address

https://lists.archlinux.org/pipermail/arch-dev-public/2021-June/030462.html

Update mailing list address
c8d88464 · Jelle van der Waa · 959e5351 · c8d88464
Verified Commit c8d88464 authored 3 years ago by Jelle van der Waa
--- a/CONTRIBUTING.md
+++ b/CONTRIBUTING.md
 # Contributing

-Patches should be sent to the [aur-dev@archlinux.org][1] mailing list.
+Patches should be sent to the [aur-dev@lists.archlinux.org][1] mailing list.

 Before sending patches, you are recommended to run `flake8` and `isort`.