Bug-821703 - Remove the redundant MP3 voice navigation files from the maps app

The app contains identical OGG and MP3 files for voice navigation, in B2G the OGG files are used automatically so the MP3s are redundant. I've modified the pre-existing application.zip file by removing the MP3 files:

- fw/audio/mi_audio.mp3
- fw/audio/km_audio.mp3

I've also adjusted this snippet in combined.js:

m=a.platform.firefox?".ogg":".mp3";

To look like this:

m=".ogg"

This should force the app to always pick the OGG files as an extra safety measure.