Loosen dependencies on ipykernel, ipywidgets, and voila ⬇️

[namurphy]

This PR loosens requirements on ipykernel, ipywidgets, and voila to be consistent with what is used by Google Colab, which is currently v5.5.6. See #2655 the motivation why.

We should strive to keep the minimum version of ipykernel to be no greater than the version used by Google Colab (which tends to run older versions of a bunch of packages, and also Python).

[namurphy]

Got this error:

 Traceback (most recent call last):
  File "D:\a\PlasmaPy\PlasmaPy\.nox\tests-3-10-lowest-direct\lib\site-packages\_pytest\config\__init__.py", line 802, in import_plugin
    __import__(importspec)
ModuleNotFoundError: No module named 'pytest_tornasync'

Related to voila-dashboards/voila#728; will bump the voila requirement to after this was resolved.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 95.23%. Comparing base (e4b3847) to head (0505118).

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #2705   +/-   ##
=======================================
  Coverage   95.23%   95.23%           
=======================================
  Files         104      104           
  Lines        9399     9399           
  Branches     2155     2155           
=======================================
  Hits         8951     8951           
  Misses        272      272           
  Partials      176      176           

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