[fix] client/simple: insecure ctx clipboard copy

Uses the deprecated [`execCommand()`](https://developer.mozilla.org/en-US/docs/Web/API/Document/execCommand)
to copy content to clipboard if accessing the instance through HTTP, this method
isn't going away soon.

Closes https://github.com/searxng/searxng/issues/5359

searx/templates/simple/elements/search_url.html

@@ -1,7 +1,7 @@
 <div id="search_url" role="complementary" aria-labelledby="search_url-title">
   <details class="sidebar-collapsible">
     <summary class="title" id="search_url-title">{{ _('Search URL') }}</summary>
-    <button id="copy_url" type="submit" data-copied-text="{{ _('Copied') }}">{{ _('Copy') }}</button>
+    <button id="copy_url" type="button" class="button" data-copied-text="{{ _('Copied') }}">{{ _('Copy') }}</button>
     <div class="selectable_url">
       <pre>{{ url_for('search', _external=True) }}?q={{ q|urlencode }}&amp;language={{ current_language }}&amp;time_range={{ time_range }}&amp;safesearch={{ safesearch }}
         {%- if pageno > 1 -%}