Bug: Incorrect IntervalIndex.is_overlapping
- [x] closes #49581 
- [x] [Tests added and passed](https://pandas.pydata.org/pandas-docs/dev/development/contributing_codebase.html#writing-tests) if fixing a bug or adding a new feature
- [x] All [code checks passed](https://pandas.pydata.org/pandas-docs/dev/development/contributing_codebase.html#pre-commit).
- [x] Added [type annotations](https://pandas.pydata.org/pandas-docs/dev/development/contributing_codebase.html#type-hints) to new arguments/methods/functions.
- [x] Added an entry in the latest `doc/source/whatsnew/vX.X.X.rst` file if fixing a bug or adding a new feature.


Also, is `pandas/_libs/intervaltree.pxi.pdf` supposed to be committed? @mroeschke Fixed.

Edit: Strangely it fails the "Python Dev / actions-311-dev (macOS-latest) (pull_request)" integration test.
Edit: Now passed. > Could you remove `pandas/_libs/intervaltree.pxi.pdf`?

I've removed this file, is there any thing I've to do now? thanks @Hikipeko 