Fix typos in documentation

[larrybradley]

The second commit also replaces tabs with spaces in using_datamodels.rst.

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:

Project coverage is 97.27%. Comparing base (087a60d) to head (95182b4). Report is 15 commits behind head on main.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #340 +/- ## ========================================== - Coverage 97.56% 97.27% -0.29% ========================================== Files 30 31 +1 Lines 2788 3048 +260 ========================================== + Hits 2720 2965 +245 - Misses 68 83 +15 ```

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[larrybradley]

I don't have repo permissions to label or merge this PR.

[larrybradley]

The pre-commit codespell test failed due to a typo in the changelog, so I just fixed that one too. :smile:

[PaulHuwe]

Let me know when you are ready for this to be merged.

[larrybradley]

Merge away!