Update info about 2.0 on Roadmap

[stpaultim]

We were just discussing in Zulip that this page may make it seem like we have missed some deadlines. Maybe the text could be updated to better reflect current thinking on 2.0.

[quicksketch]

I had proposed forking for Backdrop 2.x at the last Backdrop LIVE and the discussion that ensued indicated that no one present (other than myself) felt that creating Backdrop 2.x had sufficient value at the point. As Drupal 7 keeps living on and on, dropping compatibility layers we have in place to ease coming from Drupal 7 was not a popular suggestion. And if we can't drop Backwards-Compatibility layers yet, there's little reason to make 2.x when we can continue adding features to 1.x through minor releases.

So as to say, right now we have no planned date for even creating a 2.x branch, let alone make a 2.0 release. That does not indicate we're not actively developing Backdrop or that new features aren't being released.

So all this to say, +1, we need updating messaging around Backdrop 2.x.