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/data/misc/mobile-broadband-provider-info/default.nix

@@ -18,6 +18,6 @@ stdenv.mkDerivation rec {
     homepage = http://live.gnome.org/NetworkManager/MobileBroadband/ServiceProviders;
     platforms = stdenv.lib.platforms.all;
     license = stdenv.lib.licenses.publicDomain;
-    maintainers = [ stdenv.lib.maintainers.urkud ];
+    maintainers = [ ];
   };
 }

pkgs/data/misc/poppler-data/default.nix

@@ -19,6 +19,6 @@ stdenv.mkDerivation rec {
     description = "Encoding files for Poppler, a PDF rendering library";
     platforms = platforms.all;
     license = licenses.free; # more free licenses combined
-    maintainers = with maintainers; [ urkud ];
+    maintainers = with maintainers; [ ];
   };
 }

pkgs/data/misc/shared-desktop-ontologies/default.nix

@@ -20,7 +20,7 @@ stdenv.mkDerivation rec {
       are used by projects like KDE or Strigi.
     '';
     platforms = platforms.all;
-    maintainers = [ maintainers.sander maintainers.urkud ];
+    maintainers = [ maintainers.sander ];
   };
 }