CLN: Replace format with f-strings in test_repr_info
Updated `pandas/tests/frame/test_repr_info.py` to use f-strings

ref: https://github.com/pandas-dev/pandas/issues/29547

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

thanks!