fix(fw): EOF - Fix EXCHANGE's data_portion_length

[pdobacz]

🗒️ Description

Just a minor issue I've noticed. It didn't affect any bytecode generation, but fixing anyway

🔗 Related Issues

NA

✅ 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.

[pdobacz]

late thought - one could also derive it dynamically as len(data_portion_formatter(args)) in __getitem__, please advise if this is better. This should cover RJUMPV as well then.

[danceratopz]

Hi @pdobacz, the initial CI fail has been fixed by #850 so I merged main into this branch. Sorry about that.