MNT: pin max version of ipywidgets

[kecnry]

Description

This pull request pins the max version of ipywidgets until we can fix support with ipywidgets 8.0

Checklist for package maintainer(s)

This checklist is meant to remind the package maintainer(s) who will review this pull request of some common things to look for. This list is not exhaustive.

• Are two approvals required? Branch protection rule does not check for the second approval. If a second approval is not necessary, please apply the trivial label.
• Do the proposed changes actually accomplish desired goals? Also manually run the affected example notebooks, if necessary.
• Do the proposed changes follow the STScI Style Guides?
• Are tests added/updated as required? If so, do they follow the STScI Style Guides?
• Are docs added/updated as required? If so, do they follow the STScI Style Guides?
• Did the CI pass? If not, are the failures related?
• Is a change log needed? If yes, is it added to CHANGES.rst?
• Is a milestone set?
• After merge, any internal documentations need updating (e.g., JIRA, Innerspace)?

[codecov]

Codecov Report

Merging #1591 (5ac6fe4) into main (2c8d971) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##             main    #1591   +/-   ##
=======================================
  Coverage   85.74%   85.74%           
=======================================
  Files          94       94           
  Lines        9290     9290           
=======================================
  Hits         7966     7966           
  Misses       1324     1324           

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[pllim]

Since you found the actual compat problem, should we just turn this PR into compat fix?

jupyter-widgets/ipywidgets#3122

[kecnry]

Attempt to support ipywidgets 7 and 8 by trying to access ._active_widgets and falling back on .widgets: #1592

[pllim]

Since compatibility fix is in another PR, let's get this in now. Thanks!