Remove outdated justification for Ubuntu's exclusion from PRISM Break

Update en.json to remove the justification for excluding Ubuntu in PRISM Break's recommendations:

Canonical’s Ubuntu is not recommended by PRISM Break because it contains Amazon ads and data leaks by default. GNU/Linux distributions based on Ubuntu are also currently not recommended due to several other reasons.

It's possible that the misgivings aired here about privacy in Ubuntu may still hold true today, but the reference to "Amazon ads and data leaks" is no longer factually correct.

The statement links to a 2013 EFF article regarding the Ubuntu 12.10 release, which had a Unity desktop with Amazon integration.

But it's 2020 now, Ubuntu 20.04 will soon be released, and Ubuntu hasn't shipped with Unity for many years since.

I'm not recommending Ubuntu for inclusion, but we should at least update our reasons for excluding it. In the meantime, let's remove the inaccurate statement.