BUG: `assert_extension_array_equal` using the wrong dtype
- [x] closes #55730 
- [ ] All [code checks passed](https://pandas.pydata.org/pandas-docs/dev/development/contributing_codebase.html#pre-commit).
- [x] Added an entry in the latest `doc/source/whatsnew/v2.1.3.rst` file if fixing a bug or adding a new feature.

Thanks @rob-sil 