docs: [storagetransfer] add default values to quickstart (#4037)

* add samples to quickstart

* 🦉 Updates from OwlBot post-processor

See https://github.com/googleapis/repo-automation-bots/blob/main/packages/owl-bot/README.md

* fix copyright

---------

Co-authored-by: Owl Bot <gcf-owl-bot[bot]@users.noreply.github.com>

packages/google-storagetransfer/samples/generated/v1/snippet_metadata.google.storagetransfer.v1.json

@@ -1,7 +1,7 @@
 {
     "clientLibrary": {
         "name": "nodejs-storagetransfer",
-        "version": "2.3.0",
+        "version": "2.3.1",
         "language": "TYPESCRIPT",
         "apis": [
             {

packages/google-storagetransfer/samples/quickstart.js

@@ -1,3 +1,5 @@
+// Copyright 2023 Google LLC
+//
 // Licensed under the Apache License, Version 2.0 (the "License");
 // you may not use this file except in compliance with the License.
 // You may obtain a copy of the License at
@@ -13,7 +15,11 @@
 
 'use strict';
 
-async function main(projectId = 'my-project', gcsSourceBucket, gcsSinkBucket) {
+async function main(
+  projectId = 'my-project',
+  gcsSourceBucket = 'my-source-bucket',
+  gcsSinkBucket = 'my-sink-bucket'
+) {
   // [START storagetransfer_quickstart]
 
   // Imports the Google Cloud client library