CLN: core/dtypes/cast.py::maybe_casted_values
- [ ] closes #xxxx
- [ ] tests added / passed
- [x] passes `black pandas`
- [x] passes `git diff upstream/master -u -- "*.py" | flake8 --diff`
- [ ] whatsnew entry

xref https://github.com/pandas-dev/pandas/pull/36985#issuecomment-705804862
@jbrockmendel @jreback this is the follow-up to #36985. It seems like it's ok to just drop the special casing for EAs in `maybe_casted_values` great thanks @arw2019 