treewide: remove unused with statements from maintainer lists

$ find -type f -name '*.nix' -print0 | xargs -P "$(nproc)" -0 sed -i \
  -e 's!with lib.maintainers; \[ *\];![ ];!' \
  -e 's!with maintainers; \[ *\];![ ];!'

pkgs/development/python2-modules/futures/default.nix

@@ -22,6 +22,6 @@ buildPythonPackage rec {
     description = "Backport of the concurrent.futures package from Python 3.2";
     homepage = "https://github.com/agronholm/pythonfutures";
     license = licenses.bsd2;
-    maintainers = with maintainers; [  ];
+    maintainers = [ ];
   };
 }