fix(fw,tests): Fix Op.DATALOADN stack

[pdobacz]

🗒️ Description

Fixes the DATALOADN stack specs in opcode.py, also removes the workarounds in one test

🔗 Related Issues

N/A

✅ Checklist

• [ ] All: Set appropriate labels for the changes.
• [ ] All: Considered squashing commits to improve commit history.
• [ ] All: Added an entry to CHANGELOG.md.
• [ ] All: Considered updating the online docs in the ./docs/ directory.
• [ ] Tests: All converted JSON/YML tests from ethereum/tests have been added to converted-ethereum-tests.txt.
• [ ] Tests: A PR with removal of converted JSON/YML tests from ethereum/tests have been opened.
• [ ] Tests: Included the type and version of evm t8n tool used to locally execute test cases: e.g., ref with commit hash or geth 1.13.1-stable-3f40e65.
• [ ] Tests: Ran mkdocs serve locally and verified the auto-generated docs for new tests in the Test Case Reference are correctly formatted.