kconfig: nconf: remove meaningless wattrset() call from show_menu()

This attribute is not used because it will be overridden some lines
below:

  wattrset(main_window, attr_main_menu_box);

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>

scripts/kconfig/nconf.c

@@ -953,7 +953,6 @@ static void show_menu(const char *prompt, const char *instructions,
 	current_instructions = instructions;
 
 	clear();
-	wattrset(main_window, attr_normal);
 	print_in_middle(stdscr, 1, 0, getmaxx(stdscr),
 			menu_backtitle,
 			attr_main_heading);