Add the list of boards removed after the 4.18 release and update
other text.
Signed-off-by: Martin Roth <gaumless@gmail.com>
Change-Id: Id90a84eb9a417836a7d3fdd9b6f2f3ae34c95fc4
Reviewed-on: https://review.coreboot.org/c/coreboot/+/71530
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Felix Singer <felixsinger@posteo.net>
