Consider installing `just` with `apt-get` on Ubuntu 24.04 runners

[alarthast]

The action currently use the install-just.sh script committed to this repo to install just on the GitHub CI runners.

The benefit of using the script (which is pretty much a copy of https://github.com/casey/just/blob/master/www/install.sh) is that it supports installation on Windows, MacOS and Linux CI runners. The script downloads just from GitHub and fetches the specified version, which at the time of writing is 1.34.0:

setup-action/action.yml

Line 44 in 93841f2

bash "${{ github.action_path }}"/install-just.sh --to "$HOME/bin" --tag 1.34.0

setup-action/install-just.sh

Lines 32 to 33 in 93841f2

	url=https://github.com/casey/just
	releases=$url/releases

We previously preferred the use of the installation script to fetch just directly from GitHub over delegating to third parties such as uv or setup-just.

On Ubuntu 24.04 (but not Ubuntu 22.04), just can be installed with apt get. Perhaps installing just via Ubuntu would be more secure than fetching it from https://github.com/casey/just/releases in terms of the likelihood of a vulnerable / compromised release of just ending up in our runners.

We should consider installing just via apt get on Ubuntu 24.04 runners, and only use the install-just.sh script for Windows, MacOS and Ubuntu 22.04 runners. This could potentially reduce the attack surface of our services.