Update configuration and dependencies for documentation

[WeisLeDocto]

The last major update for the documentation was already one to two years ago. It was more than time to switch to newer pinned versions for sphinx and the doc dependencies. Along with this update, several improvements were brought to the docs:

• The documentation build was switched to nitpicky mode, to better detect broken references
• The build OS for the online documentation was updated to Ubuntu 24.04
• Some code-blocks containing forbidden characters were corrected
• The conf.py file was updated to include all possible parameters
• The broken links and references found in the docs were fixed