MAGETWO-36275: Create /mine API for BillingAddressManagement

 - removed unused local variable

Author: Cari Spruiell

dev/tests/api-functional/testsuite/Magento/Quote/Api/BillingAddressManagementTest.php

@@ -170,8 +170,6 @@ public function testGetMyAddress()
             AddressInterface::KEY_EMAIL => $address->getEmail()
         ];
 
-        $cartId = $quote->getId();
-
         $serviceInfo = [
             'rest' => [
                 'resourcePath' => self::RESOURCE_PATH . 'mine/billing-address',