t4kcommon: drop aanderse as maintainer

pkgs/by-name/t4/t4kcommon/package.nix

···
     description = "Library of code shared between tuxmath and tuxtype";
     homepage = "https://github.com/tux4kids/t4kcommon";
     license = licenses.gpl3Plus;
-    maintainers = [ maintainers.aanderse ];
+    maintainers = [ ];
     platforms = platforms.linux;
   };
 }