Docs: rerun notebooks

[mgovers]

The last run of the notebooks was a long time ago and some examples were actually outdated.

This PR fixes that

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[vincentkoppen]

Finally had a look at this PR an discussed with @nitbharambe about the difference in setup between PGM and PGM-DS in this regards.

We currently let readthedocs run the notebooks on each merge / PR, so this way I would prefer an notebook that has not been run in stead. Since read the docs will do it for us.
After looking into the current setup, I do see that our PR's do not error if a docs fails to run. This will be implemented with #169 (still WIP since we had a notebook that currently failed!).

Given our setup, do you still have a reason/strong preference that each notebook should be in the repo with a run state?

[vincentkoppen]

Closing since we automatically run notebooks now and each PR will give an error if any of them fail. So documentation should always be up to date.