Fix typo in README

Author: stefandoorn

README.md

@@ -664,7 +664,7 @@ In the example $return is used to show how a return could be handled.
     $shipment->setReferenceNumber($referenceNumber);
 
     // Set payment information
-    $shipment->setPaymentInformation(new \Ups\Entity\PaymentInformation('prepaid', (object)array('AccountNumber' => 'XX)));
+    $shipment->setPaymentInformation(new \Ups\Entity\PaymentInformation('prepaid', (object)array('AccountNumber' => 'XX')));
 
     // Ask for negotiated rates (optional)
     $rateInformation = new \Ups\Entity\RateInformation;