TST: specutils 2.0 now in main

[pllim]

Description

Similar to:

• TST: specutils 2.0 now in main astropy/specreduce#272

[github-actions]

Thank you for your contribution! 🌌 This checklist is meant to remind the package maintainers who will review this pull request of some common things to look for.

• Do the proposed changes actually accomplish desired goals?
• Do the proposed changes follow the STScI coding guidelines?
• Are tests added/updated as required? If so, do they follow the STScI testing guidelines?
• Are docs added/updated as required?
• Is rebase and/or squash necessary? If so, please provide the author with appropriate instructions.
• Did the CI pass? If no, are the failures related?
• Is a change log needed?

[github-actions]

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 97.14%. Comparing base (f0b162e) to head (b89db64).
Report is 13 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #417      +/-   ##
==========================================
- Coverage   97.18%   97.14%   -0.04%     
==========================================
  Files          17       18       +1     
  Lines        2026     2035       +9     
==========================================
+ Hits         1969     1977       +8     
- Misses         57       58       +1     

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