[HttpFoundation] Removed useless check if self::$trustProxies is set

In Request::getClientIps() on line 772 there is a check if self::$trustedProxies is not set. If this condition evaluates to true the method will return.
Because of this the second identical check on line 783 will never evaluate to true, as when reaching this position self::$trustedProxies must be set.