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/python-modules/Cython/default.nix

@@ -59,7 +59,7 @@ in buildPythonPackage rec {
 
   meta = {
     description = "An optimising static compiler for both the Python programming language and the extended Cython programming language";
-    homepage = http://cython.org;
+    homepage = https://cython.org;
     license = lib.licenses.asl20;
     maintainers = with lib.maintainers; [ fridh ];
   };