Treewide: update some problematic homepages

These URLs are reported as problematic by Repology.
It could be a permanent redirection
or the page does not exist anymore

pkgs/development/python-modules/opt-einsum/2.nix

@@ -23,7 +23,7 @@ buildPythonPackage rec {
 
   meta = {
     description = "Optimizing NumPy's einsum function with order optimization and GPU support.";
-    homepage = http://optimized-einsum.readthedocs.io;
+    homepage = "https://optimized-einsum.readthedocs.io";
     license = lib.licenses.mit;
     maintainers = with lib.maintainers; [ teh ];
   };