Dropping Support for Ubuntu 20.04 arm64 containers in Release v23.06

Overview

Due to a bug in glibc 2.31 (https://bugzilla.redhat.com/show_bug.cgi?id=1722181) with no current workaround, we are unable to publish arm64 ubuntu20.04 containers effective RAPIDS release 23.04. x86_64 containers are not affected. More details may be found in the tracking issue: https://github.com/rapidsai/docker/pull/551

Impact

arm64 users should migrate to ubuntu22.04 as soon as possible.