[APT] Fix "some indexes failed to download" error

If you ever encounter this APT error:

some indexes failed to download (E: Some index files failed to download. They have been ignored, or old ones used instead.)

It might mean that your local APT info somehow was messed up but you can easily fix this by purging it and asking APT to update it again:

sudo rm -vf /var/lib/apt/lists/*
apt-get update