BUG: raise ValueError when sep and delimiter are defined in read_csv
- [x] closes #39823
- [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

cc @gfyoung if any comments @phofl can you rebase and will look again merged master thanks @phofl 