Update actions to work on ubuntu-latest

[lauramurgatroyd]

Description

When we have ubuntu latest CI is currently failing on github because there is no module named cil https://github.com/TomographicImaging/CIL/actions/runs/12349560947/job/34461234403

Last time the actions passed was when they were running on Ubuntu 22.04.5. ubuntu-latest recently updated which version its using to Ubuntu 24.04.1 and this is when our actions started failing

actions/runner-images#10636

If you see any issues with your workflows during transition period:
Switch back to Ubuntu 22 by changing workflow YAML to use runs-on: ubuntu-22.04 We support two latest LTS Ubuntu versions, so Ubuntu 22 will still be maintained for the next 2 years.

Therefore our temporary fix has been to use ubuntu 22 #2016 for now but we need to update so it works on ubuntu latest

The error seems to be originated by CMake not picking the right python. conda installs python 3.10 while the install directory is /usr/local/lib/python3.12/dist-packages/cil meaning that the the wrong python is picked by CMake.

Environment

import cil, sys
print(cil.version.version, cil.version.commit_hash, sys.version, sys.platform)