corrected test url

Author: zdary

src/RelayPay.php

@@ -11,7 +11,7 @@
 use RelayPay\SDK\Api\Transactions;
 
 class RelayPay {
-	const URL_TEST = 'https://sandbox-api.relaypay.io';
+	const URL_TEST = 'https://api.sandbox.relaypay.io';
 	const URL_PROD = 'https://api.relaypay.io';
 
 	private $client;