Outdated basic example

The example at https://higgs-dna.readthedocs.io/en/latest/notebooks/basics.html is outdated and should be fixed. This needs to be revamped anyways when we fully move to coffea 2023, though. But we should fix it so that it is not hanging around there as an incorrect example until ~April.

Actually, it might also be a good idea to move something like this to tests to ensure that we are not breaking our processors!