[fix] simple theme: description of HTTP method

Suggested-by: @not-my-profile https://github.com/searxng/searxng/pull/754#issuecomment-1012921096
Signed-off-by: Markus Heiser <markus.heiser@darmarit.de>

searx/templates/simple/preferences.html

@@ -241,7 +241,7 @@
           <option value="GET" {% if method == 'GET' %}selected="selected"{% endif %}>GET</option>
         </select>
       </p>
-      <div class="description">{{ _('Search language') }}</div>
+      <div class="description">{{ _('Change how forms are submited, <a href="http://en.wikipedia.org/wiki/Hypertext_Transfer_Protocol#Request_methods" rel="external">learn more about request methods</a>') }}</div>
     </fieldset>
     {% endif %}
     {% if 'image_proxy' not in locked_preferences %}