DEPR: Raise FutureWarning when creating empty series without dtype
- [x] closes #30017
- [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

Note, this would make the next release 1.4 for sure.

thanks @lithomas1 very nice! yeah i guess we should have done this a while back, but better late than not!