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/jupyterlab/default.nix

@@ -28,7 +28,7 @@ buildPythonPackage rec {
   meta = with lib; {
     description = "Jupyter lab environment notebook server extension.";
     license = with licenses; [ bsd3 ];
-    homepage = "http://jupyter.org/";
+    homepage = "https://jupyter.org/";
     maintainers = with maintainers; [ zimbatm costrouc ];
   };
 }