treewide: Change URLs to HTTPS

Lots of URLs were HTTP redirect to HTTPS. Changed those and checked them
if there's actual content. Inspired by
https://github.com/NixOS/nixpkgs/issues/60004

pkgs/development/libraries/faad2/default.nix

@@ -17,7 +17,7 @@ stdenv.mkDerivation rec {
 
   meta = {
     description = "An open source MPEG-4 and MPEG-2 AAC decoder";
-    homepage    = http://www.audiocoding.com/faad2.html;
+    homepage    = https://www.audiocoding.com/faad2.html;
     license     = licenses.gpl2;
     maintainers = with maintainers; [ codyopel ];
     platforms   = platforms.all;