DOC: add note to how pandas deduplicate header when read from file
- [ ] closes #57792 (Replace xxxx with the GitHub issue number)
- [ ] [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
- [ ] All [code checks passed](https://pandas.pydata.org/pandas-docs/dev/development/contributing_codebase.html#pre-commit).
- [ ] Added [type annotations](https://pandas.pydata.org/pandas-docs/dev/development/contributing_codebase.html#type-hints) to new arguments/methods/functions.
- [ ] Added an entry in the latest `doc/source/whatsnew/vX.X.X.rst` file if fixing a bug or adding a new feature.

<img width="904" alt="image" src="https://github.com/pandas-dev/pandas/assets/30631476/3d5ee26f-8b6c-4493-bcfd-5491cd68417d">


/preview Website preview of this PR available at: https://pandas.pydata.org/preview/pandas-dev/pandas/57874/ Thanks @quangngd 