Interactive fitting widgets broken

[MarJMue]

The new Version of Plotly or the switch to anywidget silently breaks our jupyter notebooks.
I will try to find out what is going wrong.

[domna]

Should we just set the plotly version below the problematic version in pyproject.toml for now? Seems that this is a blind spot in the tests, too.

[MarJMue]

This is the problem:

Pinning to plotly<6 seems to work. Should be best to pin it for now.