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/mpi4py/default.nix

@@ -46,7 +46,7 @@ buildPythonPackage rec {
   meta = {
     description =
       "Python bindings for the Message Passing Interface standard";
-    homepage = http://code.google.com/p/mpi4py/;
+    homepage = "https://bitbucket.org/mpi4py/mpi4py/";
     license = stdenv.lib.licenses.bsd3;
   };
 }