Fix erasure of Integrator subsytem, remove OpenMDAO upper bound

[A-CGray]

Purpose

Fixes OpenMDAO/OpenMDAO#3621, making OpenConcept compatible with latest version of OpenMDAO.

Type of change

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• - Bugfix (non-breaking change which fixes an issue)
• - New feature (non-breaking change which adds functionality)
• - Breaking change (non-backwards-compatible fix or feature)
• - Code style update (formatting, renaming)
• - Refactoring (no functional changes, no API changes)
• - Documentation update
• - Other (please describe)

Testing

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Checklist

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• I have run unit and regression tests which pass locally with my changes
• I have added new tests that prove my fix is effective or that my feature works
• I have added necessary documentation

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 82.03%. Comparing base (82bdf26) to head (650385d).
⚠️ Report is 2 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #83      +/-   ##
==========================================
- Coverage   82.04%   82.03%   -0.02%     
==========================================
  Files         103      103              
  Lines       10724    10724              
==========================================
- Hits         8799     8797       -2     
- Misses       1925     1927       +2     

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[A-CGray]

Failing tests are being caused by pyCycle, I've opened this PR to fix the issue

[A-CGray]

@kanekosh OpenMDAO/pyCycle#109 is now merged, but we need to wait for a new pyCycle release to be made before our tests will pass