Update to v4.9.8.md

Upgrade Guide

For steps 1 and 2 the instructions are the same for iOS and Android.

1. Update to the latest version of the push notifications script
2. Update to the latest version of the Firebase Rules file.
3. Update to the latest version of the library:
   iOS - 4.9.8
   Android - 4.6.0
4. Update your modules from your user account page.