move ipywidgets to docs dependency group

[sbidari]

Should've noticed this yesterday but I think ipywidgets should be in docs dependency to prevent warnings (see below) in the tutorials

/home/runner/.cache/pypoetry/virtualenvs/multisignal-epi-inference-vAaUqUWX-py3.12/lib/python3.12/site-packages/tqdm/auto.py:21: TqdmWarning: IProgress not found. Please update jupyter and ipywidgets. See https://ipywidgets.readthedocs.io/en/stable/user_install.html
  from .autonotebook import tqdm as notebook_tqdm

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 93.23%. Comparing base (d8e9f5d) to head (d132b84).

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #352   +/-   ##
=======================================
  Coverage   93.23%   93.23%           
=======================================
  Files          39       39           
  Lines         917      917           
=======================================
  Hits          855      855           
  Misses         62       62           

Flag	Coverage Δ
unittests	93.23% <ø> (ø)

Flags with carried forward coverage won't be shown. Click here to find out more.

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.