CONTRIBUTING.md: switch to a link that actually works

vcunat · vcunat · commit 0d2620961fff · 2016-11-24T10:03:13.000+01:00
Fixes #20594. (cherry picked from commit b59167c) Also another link was switched from Hydra to https://nixos.org.
diff --git a/.github/CONTRIBUTING.md b/.github/CONTRIBUTING.md
@@ -28,5 +28,8 @@ under the terms of [COPYING](../COPYING), which is an MIT-like license.
   * Not start with the package name
   * Not have a dot at the end
 
-See the nixpkgs manual for more details on how to [Submit changes to nixpkgs](http://hydra.nixos.org/job/nixpkgs/trunk/manual/latest/download-by-type/doc/manual#chap-submitting-changes).
+See the nixpkgs manual for more details on how to [Submit changes to nixpkgs](https://nixos.org/nixpkgs/manual/#chap-submitting-changes).
 
+## Reviewing contributions
+
+See the nixpkgs manual for more details on how to [Review contributions](https://nixos.org/nixpkgs/manual/#sec-reviewing-contributions).
