Warnings and extraneous outputs in validation section of jupyterbook docs

https://policyengine.github.io/openfisca-uk//model/validation.html#aggregates-in-full

<img width="940" alt="image" src="https://user-images.githubusercontent.com/6076111/165431551-50c46fdb-c2a6-4672-b481-890e50fa204b.png">
