treewide: purge maintainers.urkud

It's sad, but he's been inactive for the last five years.
Keeping such people in meta.maintainers is counter-productive.

pkgs/development/libraries/atk/default.nix

@@ -39,7 +39,7 @@ stdenv.mkDerivation rec {
 
     license = stdenv.lib.licenses.lgpl2Plus;
 
-    maintainers = with stdenv.lib.maintainers; [ raskin urkud ];
+    maintainers = with stdenv.lib.maintainers; [ raskin ];
     platforms = stdenv.lib.platforms.linux ++ stdenv.lib.platforms.darwin;
   };