ansible: update OSUOSL hosted arm64 Docker host

[richardlau]

Update and rename test-osuosl-ubuntu2004-docker_arm64-1 to Ubuntu 24.04.

Fixes: #4227

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I updated the instance by renaming it in OpenStack and then rebuilding it with an Ubuntu 24.04 image.
Had an issue with the hostname -- it kept resetting back to the original name when restarting the VM. In the end I added a file /etc/cloud/cloud.cfg.d/99_hostname.cfg with

#cloud-config
hostname: test-osuosl-ubuntu2404-docker-arm64-1
fqdn: test-osuosl-ubuntu2404-docker-arm64-1.novalocal

I haven't done that in Ansible because it should not be necessary if provisioning a new instance (as opposed to rebuilding the existing one).