CLN: C408 Unnecessary dict call - rewrite as a literal #38138
Fix in:
./pandas/tests/io/generate_legacy_storage_files.py

- [x] closes #38138
- [x] tests added / passed
- [x] passes `black pandas`
- [x] passes `git diff upstream/master -u -- "*.py" | flake8 --diff`
- [x] whatsnew entry
