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/eigen/2.0.nix

@@ -18,7 +18,7 @@ stdenv.mkDerivation {
     description = "C++ template library for linear algebra: vectors, matrices, and related algorithms";
     license = licenses.lgpl3Plus;
     homepage = http://eigen.tuxfamily.org ;
-    maintainers = with stdenv.lib.maintainers; [ sander urkud raskin ];
+    maintainers = with stdenv.lib.maintainers; [ sander raskin ];
     branch = "2";
     platforms = with stdenv.lib.platforms; unix;
   };

pkgs/development/libraries/eigen/3.3.nix

@@ -19,7 +19,7 @@ stdenv.mkDerivation {
     license = licenses.lgpl3Plus;
     homepage = http://eigen.tuxfamily.org ;
     platforms = platforms.unix;
-    maintainers = with stdenv.lib.maintainers; [ sander urkud raskin ];
+    maintainers = with stdenv.lib.maintainers; [ sander raskin ];
     inherit version;
   };
 }

pkgs/development/libraries/eigen/default.nix

@@ -23,7 +23,7 @@ stdenv.mkDerivation {
     license = licenses.lgpl3Plus;
     homepage = http://eigen.tuxfamily.org ;
     platforms = platforms.unix;
-    maintainers = with stdenv.lib.maintainers; [ sander urkud raskin ];
+    maintainers = with stdenv.lib.maintainers; [ sander raskin ];
     inherit version;
   };
 }