CLN: remove try/except in _prep_ndarray
- [ ] closes #xxxx
- [ ] tests added / passed
- [ ] 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

Recent-ish edits to the `convert` function make the fallback unnecessary.
nice ping on green ping