TST: Verify plot order of a Series (GH38865)
- [x] closes #38865
- [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
- [x] whatsnew entry

Verified that the test passes on master, but fails on version 1.2.0 as expected CI is greenish. Failure due to another issue not related to this PR. thanks @avinashpancham 