Remove psutil dependency

[WilliamJamieson]

This PR fixes #318 by removing the unused psutil dependency.

Checklist

• [ ] Added entry in CHANGES.rst under the corresponding subsection
• [ ] updated relevant tests
• [ ] updated relevant documentation
• [ ] Passed romancal regression testing on Jenkins / PLWishMaster. Link: https://plwishmaster.stsci.edu:8081/job/RT/job/romancal/XXX/

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Comparison is base (719262c) 97.58% compared to head (e8be840) 97.58%.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #320 +/- ## ======================================= Coverage 97.58% 97.58% ======================================= Files 31 31 Lines 2810 2810 ======================================= Hits 2742 2742 Misses 68 68 ```

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