make rotation matrix 2d for schema validation

[stscieisenhamer]

This PR addresses an issue found during HLP development. If a rotation matrix needs to be calculated, in order to populate the wcsinfo block, the resultant form was not compatible with the schema. This PR fixes that formatting.

Checklist

• [x] added entry in CHANGES.rst under the corresponding subsection
• [ ] updated relevant tests
• [x] updated relevant documentation
• [ ] updated relevant milestone(s)
• [x] added relevant label(s)
• [ ] ran regression tests, post a link to the Jenkins job below. How to run regression tests on a PR

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 25.00000% with 3 lines in your changes are missing coverage. Please review.

Project coverage is 77.47%. Comparing base (2df177e) to head (103cf85). Report is 15 commits behind head on main.

Files	Patch %	Lines
romancal/resample/resample.py	0.00%	2 Missing :warning:
romancal/assign_wcs/utils.py	50.00%	1 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #1205 +/- ## ========================================== + Coverage 77.15% 77.47% +0.32% ========================================== Files 107 109 +2 Lines 7101 7362 +261 ========================================== + Hits 5479 5704 +225 - Misses 1622 1658 +36 ``` | [Flag](https://app.codecov.io/gh/spacetelescope/romancal/pull/1205/flags?src=pr&el=flags&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=spacetelescope) | Coverage Δ | | *Carryforward flag | |---|---|---|---| | [nightly](https://app.codecov.io/gh/spacetelescope/romancal/pull/1205/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=spacetelescope) | `62.80% <ø> (ø)` | | Carriedforward from [2df177e](https://app.codecov.io/gh/spacetelescope/romancal/commit/2df177ed8ffe364919e811cb79d4733ad32ffb6c?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=spacetelescope) | *This pull request uses carry forward flags. [Click here](https://docs.codecov.io/docs/carryforward-flags?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=spacetelescope) to find out more.

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