revert changin about to searx docs

searx/templates/simple/base.html

   </main>
   <footer>
     <p>
-        {{ _('Powered by') }} <a href="https://asciimoo.github.io/searx/">searx</a> - {{ searx_version }} - {{ _('a privacy-respecting, hackable metasearch engine') }}<br/>
+    {{ _('Powered by') }} <a href="{{ url_for('about') }}">searx</a> - {{ searx_version }} - {{ _('a privacy-respecting, hackable metasearch engine') }}<br/>
         <a href="https://github.com/asciimoo/searx">{{ _('Source code') }}</a> |
         <a href="https://github.com/asciimoo/searx/issues">{{ _('Issue tracker') }}</a> |
         <a href="https://github.com/asciimoo/searx/wiki/Searx-instances">{{ _('Public instances') }}</a>