Update front page to better explain g.d.o's status

Problem / motivation

The front page of groups.drupal.org has a news feed that is no longer managed. The last events listed are from 2020. This gives the impression that groups.drupal.org is dead, when that is not actually the case. No new features are being developed, but several groups actively use it to post events and communicate with members.

There are many links across the internet that point to groups.drupal.org, and the current appearance confuses and discourages people who are looking for Drupal groups and meetups.

The long term plan is to recreate the features of this platform on the new Drupal.org. It may take a while to achieve that, so we should raise awareness of the plan, create a good impression, and help newcomers find groups they might be interested in joining.

Suggested solution

Edit: An simpler solution may be to add a new post with the desired text and promote it to the front page, so that it appears at the top and the outdated 2020 post is moved down.

* Remove the outdated and unmanaged river of news from the front page of groups.drupal.org
* Add a statement below the green box about events that says something like the following:

"This Drupal Groups site is minimally maintained. We plan to recreate its features on the new Drupal.org, so it will be fully integrated with community events, user profiles, and Drupal.org APIs. If you would like to help with that effort, please comment on this issue #3048700: Discontinue groups.drupal.org.

You can also find information about local groups on Find an Event: Local Communities."

Open to suggestions on the wording. The goal is to reduce confusion and let active groups continue to use g.d.o. until a replacement is ready.