Fixing scatter plot size (#32904)
This fixes the marker size in scatter plots (see https://github.com/pandas-dev/pandas/issues/32904).

- [x] closes #32904
- [ ] tests added / passed
- [x] passes `black pandas`
- [x] passes `git diff upstream/master -u -- "*.py" | flake8 --diff`
- [ ] whatsnew entry
