Don't use "with licenses;" for single licences

And don't use square brackets on such lines.

pkgs/applications/editors/vim/default.nix

@@ -49,7 +49,7 @@ stdenv.mkDerivation rec {
   meta = with stdenv.lib; {
     description = "The most popular clone of the VI editor";
     homepage    = http://www.vim.org;
-    license = with licenses; [ vim ];
+    license = licenses.vim;
     maintainers = with maintainers; [ lovek323 ];
     platforms   = platforms.unix;
   };