Login: Disable the required cue

It should be obvious that it is necessary to input a name and a password
to login in case you're looking at a "login" form...

refs #7934

application/forms/Authentication/LoginForm.php

@@ -16,6 +16,7 @@ class LoginForm extends Form
      */
     public function init()
     {
+        $this->setRequiredCue(null);
         $this->setName('form_login');
         $this->setSubmitLabel($this->translate('Login'));
     }