Until libvirt 2.5.0 we didn't have a real process for release
notes in place, and we just published the list of commits that
had made it into each release, dividing them into categories that
mostly matched the sections we use today. Those documents haven't
been relevant for years, but they're still in the git repository
and collectively take up almost 2 MiB of disk space.

Let's import the only valuable piece of information they contain,
the release date for each libvirt versions, into the current
document and then drop them for good.
Signed-off-by: NAndrea Bolognani <abologna@redhat.com>
Reviewed-by: NJán Tomko <jtomko@redhat.com>