fix issue with new client overriding set api key (#1305)

if you call `sgMail.setClient()` _before_ you call `sgMail.setApiKey()` then everything is great. If you call them in the order that this test does you'll forever get `Unauthorized` 401 section with data.headers not including `Bearer Authorization <<YOUR_API_KEY>>`

test/typescript/mail.ts

@@ -1,12 +1,12 @@
 import { Client } from "@sendgrid/client";
 import sgMail = require("@sendgrid/mail");
 
-// Test setApiKey() method
-sgMail.setApiKey("MY_SENDGRID_API_KEY");
-
 // Test setClient() method
 sgMail.setClient(new Client());
 
+// Test setApiKey() method
+sgMail.setApiKey("MY_SENDGRID_API_KEY");
+
 // Test setSubstitutionWrappers() method
 sgMail.setSubstitutionWrappers("{{", "}}")
 
@@ -276,4 +276,4 @@ sgMail.send({
   ipPoolName: 'sendgrid-ip-pool-name',
   mailSettings: {},
   trackingSettings: {},
-});
+});