android.provider.Telephony
simply doesn't exist yet (as of API 18 - 4.3).
This class will be added in 4.4 (presumably API 19), and that blog post is highlighting the changes that you should make once the new API is released so you aren't surprised when the time comes.
From the end of the post:
To help you make the changes, we'll soon be providing the necessary SDK components for Android 4.4 that allow you to compile and test your changes on Android 4.4.
Don't forget that you should wrap this code in an API version check so you don't run into issues with older versions that don't have this class.