function plt_hide_posts_per_page_changer_ui_menus() {
//Hide the "Settings → Posts Per Page Changer UI" menu.
remove_submenu_page('options-general.php', 'posts_per_page_changer_ui_setting');
}
add_action('admin_menu', 'plt_hide_posts_per_page_changer_ui_menus', 11);