[FIX] website_portal: remove keep_query on archives

It was impossible to pass from  an archive to another because of
the keep_query in the url generated that set multiple times the
same argument in the url. Removing this allow to have a 'date_begin'
and a 'date_end' corresponding to the selected archive.

addons/website_portal/views/templates.xml

@@ -19,7 +19,7 @@
                 </t>
                 <t t-if="group['date_begin'] != date">
                     <li>
-                        <a t-ignore="True" t-attf-href="#{default_url}?#{keep_query()}&amp;date_begin=#{group['date_begin']}&amp;date_end=#{group['date_end']}"><t t-esc="group['name']"/><span class="pull-right badge" t-esc="group['item_count']"/></a>
+                        <a t-ignore="True" t-attf-href="#{default_url}?date_begin=#{group['date_begin']}&amp;date_end=#{group['date_end']}"><t t-esc="group['name']"/><span class="pull-right badge" t-esc="group['item_count']"/></a>
                     </li>
                 </t>
             </t>