treewide: remove the-kenny from maintainers

@the-kenny did a good job in the past and is set as maintainer in many package,
however since 2017-2018 he stopped contributing. To create less confusion
in pull requests when people try to request his feedback, I removed him as
maintainer from all packages.

pkgs/tools/backup/rdiff-backup/default.nix

@@ -19,6 +19,5 @@ python2Packages.buildPythonApplication {
     homepage = "http://rdiff-backup.nongnu.org/";
     license = stdenv.lib.licenses.gpl2;
     platforms = stdenv.lib.platforms.all;
-    maintainers = with stdenv.lib.maintainers; [ the-kenny ];
   };
 }