DEPR: DataFrame(floaty, dtype=inty) match Series
- [ ] closes #xxxx
- [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
- [ ] whatsnew entry

xref #40110, though we may still deprecate the Series behavior too, in which case we'll need to update the deprecation message here