Set script src (#92)

Author: nbierdeman

test/paypal.js

@@ -1,10 +1,13 @@
 /* @flow */
 
-import { setupSDK, insertMockSDKScript } from "@paypal/sdk-client/src";
+import { setupSDK } from "@paypal/sdk-client/src";
 
 import * as paypalCheckout from "../src/interface"; // eslint-disable-line import/no-namespace
 
-insertMockSDKScript();
+document.currentScript?.setAttribute(
+  "src",
+  "test.paypal.com/sdk/js?client-id=abcxyz123"
+);
 
 window.mockDomain = "mock://www.paypal.com";