[Web] fixed add domain save action button group styling

Signed-off-by: Kristian Feldsam <feldsam@gmail.com>

data/web/templates/modals/mailbox.twig

@@ -506,7 +506,6 @@
               {% if not skip_sogo %}
               <button class="btn btn-xs-lg btn-xs-half d-block d-sm-inline btn-secondary" data-action="add_item" data-id="add_domain" data-api-url='add/domain' data-api-attr='{"tags": []}' href="#">{{ lang.add.add_domain_only }}</button>
               <button class="btn btn-xs-lg btn-xs-half d-block d-sm-inline btn-secondary" data-action="add_item" data-id="add_domain" data-api-url='add/domain' data-api-attr='{"restart_sogo":"1", "tags": []}' href="#">{{ lang.add.add_domain_restart }}</button>
-              <div class="clearfix visible-xs"></div>
               {% else %}
               <button class="btn btn-xs-lg d-block d-sm-inline btn-success" data-action="add_item" data-id="add_domain" data-api-url='add/domain' data-api-attr='{"tags": []}' href="#">{{ lang.add.add }}</button>
               {% endif %}