Point reports to original URL

That way the redirects set up in ngi-nix/ngipkgs#476 can be maintained in one place rather than relying on GitHub

src/content/blog/announcements/2022-02-23-summer-of-nix-2021-report.md

@@ -4,6 +4,6 @@ date: 2021-02-23
 ---
 
 Happy to announce that the [Summer of Nix 2021 report is
-out](https://ngi-nix.github.io/summer-of-nix/SoN-2021-report.pdf). This report explains in detail the motivation
+out](https://summer.nixos.org/assets/report-2021.pdf). This report explains in detail the motivation
 behind Summer of Nix, and how it was organized in 2022. If you have comments or
 questions, don't hesitate to reach out to [email protected].

src/content/blog/announcements/2022-04-04-summer-of-nix-2022.md

@@ -8,7 +8,7 @@ Summer of Nix 2022 will happen **from July 18th to September 30th**!
 [Applications are open here from now until May 15th!](https://cryptpad.fr/form/#/2/form/view/HyAQLTXDtHy0JNGvRIwWXa6Swmxb31LuWsOoPRcmD-8/).
 
 Following the excitement of Summer of Nix 2021 (more in [last year’s
-report](https://ngi-nix.github.io/summer-of-nix/SoN-2021-report.pdf), I am happy to
+report](https://summer.nixos.org/assets/report-2021.pdf), I am happy to
 announce that the European Commission, NLNet and the NixOS Foundation have
 granted enough budget to organize another community event this year. After some
 brainstorming sessions I am excited to share how we (an organization committee