MT#5751 prevent staleelement exception when searching datatables

if this ajax call is not yet finished it changes the table, which interferes
with the commands which follow

remove it, as there should be only one row anyways

see 5751#c37733

t/controller_billing_selenium.t

@@ -139,7 +139,6 @@ $d->fill_element_ok([name => 'end', "2008-02-28 13:37:00"]);
 $d->findclick_ok(name => 'save');
 
 diag("Find/delete my created date definition");
-$d->fill_element_ok([xpath => '//div[contains(@class, "dataTables_filter")]//input', '2008-02-28']);
 $row = $d->find(xpath => '//div[contains(@class,"dataTables_wrapper")]//td[contains(text(),"2008-02-28")]/..');
 ok($row);
 $d->move_to(element => $row);