DOC: Example from docstring was proposing wrong interpolation order
Currently doctring explaining interpolation proposes using polynomial interpolation with order equal to 4. Unfortunately, scipy does not allow that value to be used, throwing an ValueError from here: https://github.com/scipy/scipy/blob/5875fd397eb4e6adcfa0c65f7b9006424c066cb0/scipy/interpolate/_bsplines.py#L583
Looking at the blame, last edit was 5 years ago so that rather do not depend on any reasonable scipy version.

Interpolations with order equal to 2 that are spread around docstrings (and doctests) do not pass through the method throwing that exception so they are okay.

- [-] closes #xxxx
- [x] tests added / passed
- [x] passes `git diff upstream/master -u -- "*.py" | flake8 --diff`
- [-] whatsnew entry
