Update CI script to use new build server and credentials.

This brings our deploy job in line with the microscope's by updating the server and using the new organization-level secret for authentication. This is a file secret rather than a variable, which should be more secure (less likely to be leaked into logs) and neater (no need to base64-encode/decode).

I have updated the path to the update-latest script (now a .sh shellscript rather than a .py Python file), and updated the path to the build artifacts.

I've also deleted the broken Zenodo job and removed the related script.

This branch now deploys correctly and is ready to merge.