TST: Adding test for checking that plotting grid param by default is mpl.rcParams['axes.grid']
- [ ] Related to #3188
- [ ] tests added to pandas/tests/plotting/test_style.py and passed
- [ ] Ensure all linting tests pass, see [here](https://pandas.pydata.org/pandas-docs/dev/development/contributing_codebase.html#pre-commit) for how to run them
- [ ] Seems the issue is obsolete. As I can see now the tested behavior is by design with matplotlib backend for visualization, but more tests is better ;)
