DOC: added note on str cons for read_sql
- [x] closes #46023  
- [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).
- [ ] Added an entry in the latest `doc/source/whatsnew/vX.X.X.rst` file if fixing a bug or adding a new feature.

Thanks for the pull request, but more information needs to be provide in the original issue before proceeding with this change.

Closing this for now, but feel free to address any other issue with `good first issue`! 