There is a time once every 2 years when ubuntu team releases new LTS
release. And then UCA joins with binary packages for current OpenStack
development cycle.

It is this time for Ubuntu 20.04 'focal'.

Includes CI fix to pass:

[CI] Temporarily block new Ansible

The proper fix [1] needs fixing older branches before newer.
This one allows to fix CI first, in the usual order.

To revert after [1] gets merged in all relevant branches.

[1] https://review.opendev.org/745648

Old-Change-Id: Ifbd37d8addd4322773118e2e9d46494741a8ae66
Related-Bug: #1891145

Depends-on: https://review.opendev.org/#/c/738994/


Change-Id: Ib8b70ee40ec2d19509cc84c0f530612f81907721
Co-Authored-By: Radosław Piliszek <radoslaw.piliszek@gmail.com>

Adds a support matrix page to documentation.

Change-Id: Ia783f7c42219617cde2accd3f1db013c9bda7679