Remove unnecessary wrapper forward_model_data_to_json

[AugustoMagalhaes]

Issue
Resolves #9545

Approach
Removes extra wrapper layer in ert_config.py (forward_model_data_to_json) and updates tests related to it.

(Screenshot of new behavior in GUI if applicable)

• PR title captures the intent of the changes, and is fitting for release notes.
• Added appropriate release note label
• Commit history is consistent and clean, in line with the contribution guidelines.
• Make sure unit tests pass locally after every commit (git rebase -i main --exec 'pytest tests/ert/unit_tests -n logical -m "not integration_test"')

When applicable

• When there are user facing changes: Updated documentation
• New behavior or changes to existing untested code: Ensured that unit tests are added (See Ground Rules).
• Large PR: Prepare changes in small commits for more convenient review
• Bug fix: Add regression test for the bug
• Bug fix: Create Backport PR to latest release

[berland]

Thanks for your contribution, this looks good!

Could up update the PR title so it becomes suitable for release notes?
Could you squash the commits (every commit must pass all tests)
(then tick of the appropriate items in the PR template)

[codspeed-hq]

CodSpeed Performance Report

Merging #9551 will improve performances by 80.71%

_{Comparing AugustoMagalhaes:ISSUE_9545 (997651b) with main (0d10c5d)}

Summary

⚡ 1 improvements
✅ 22 untouched benchmarks

Benchmarks breakdown

	Benchmark	main	AugustoMagalhaes:ISSUE_9545	Change
⚡	test_gui_snapshot	3.6 s	2 s	+80.71%

[berland]

Perfect!

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 91.86%. Comparing base (0d10c5d) to head (997651b).
Report is 2 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #9551      +/-   ##
==========================================
- Coverage   91.87%   91.86%   -0.01%     
==========================================
  Files         433      433              
  Lines       26768    26762       -6     
==========================================
- Hits        24593    24585       -8     
- Misses       2175     2177       +2     

Flag	Coverage Δ
cli-tests	39.77% <100.00%> (-0.01%)	⬇️
everest-models-test	34.66% <100.00%> (-0.01%)	⬇️
gui-tests	72.15% <100.00%> (+0.02%)	⬆️
integration-test	37.20% <100.00%> (-0.01%)	⬇️
performance-tests	51.97% <100.00%> (+<0.01%)	⬆️
test	40.48% <100.00%> (+0.01%)	⬆️
unit-tests	74.16% <100.00%> (-0.02%)	⬇️

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