[mod] typification of the preference settings

no functional change / except the missing online doc which is now available::

    $ make docs.live
    $ xdg-open "http://127.0.0.1:8000/admin/settings/settings_preferences.html"

Signed-off-by: Markus Heiser <markus.heiser@darmarit.de>

client/simple/src/js/toolkit.ts

@@ -5,7 +5,6 @@ import type { KeyBindingLayout } from "./main/keyboard.ts";
 // synced with searx/webapp.py get_client_settings
 type Settings = {
   plugins?: string[];
-  advanced_search?: boolean;
   autocomplete?: string;
   autocomplete_min?: number;
   doi_resolver?: string;