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/boltztrap2/default.nix

@@ -37,7 +37,7 @@ buildPythonPackage rec {
   '';
 
   meta = with stdenv.lib; {
-    homepage = https://www.boltztrap.org/;
+    homepage = "http://www.boltztrap.org/";
     description = "Band-structure interpolator and transport coefficient calculator";
     license = licenses.gpl3;
     maintainers = [ maintainers.costrouc ];