BUG: IntervalArray.insert cast on failure
- [ ] 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

We fixed this for DTI/TDI/PI in #39068.  Also did CategoricalIndex recently, not sure where off the top.
does it need a whatsnew note? > does it need a whatsnew note?

i think this is covered by the whatsnew note in #39068