Fix [cloud-nio] link (#3835)

Author: arifkasim

TESTING.md

@@ -348,4 +348,4 @@ Here is an example that uses the `RemoteSpannerHelper` to create a database.
 [cloud-platform-authentication]:https://cloud.google.com/docs/authentication/getting-started
 [cloud-platform-storage-authentication]:https://cloud.google.com/storage/docs/authentication?hl=en#service_accounts
 [create-service-account]:https://developers.google.com/identity/protocols/OAuth2ServiceAccount#creatinganaccount
-[cloud-nio]:https://github.com/googleapis/google-cloud-java/tree/master/google-cloud-contrib/google-cloud-nio
+[cloud-nio]:https://github.com/googleapis/google-cloud-java/tree/master/google-cloud-clients/google-cloud-contrib/google-cloud-nio