qrencode: remove SDL2 to fix infinite recursion in tests

Nix fails with an infinite recursion error When running the qrencode tests with
SDL2 in nativeCheckInputs.

Removing the dependency fixes the error and the tests still run successfully.

pkgs/by-name/qr/qrencode/package.nix

@@ -3,7 +3,6 @@
   stdenv,
   fetchFromGitHub,
   pkg-config,
-  SDL2,
   libpng,
   libiconv,
   autoreconfHook,
@@ -37,8 +36,6 @@ stdenv.mkDerivation (finalAttrs: rec {
     libpng
   ];
 
-  nativeCheckInputs = [ SDL2 ];
-
   doCheck = false;
 
   checkPhase = ''