TST: added test for to_string when max_rows is zero (GH35394)
- [x] closes #35394
- [x] tests added / passed
- [x] Ensure all linting tests pass, see [here](https://pandas.pydata.org/pandas-docs/dev/development/contributing.html#code-standards) for how to run them

Provided tests for `to_string` when `max_rows=0`.

Tests and linter pass locally.