Pin ipywidgets under 8.0.5

[eccabay]

ipywidgets 8.0.5 added this change, which led to these errors in our tests with regards to building our search iteration plots.

[bollwyvl]

A quick fix might be (e.g. in conftest.py):

import ipykernel.ipkernel  # noqa

This abuses some side-effects from importing that module.