DOC: Add to the io documentation of `on_bad_lines` to alert users of silently skipped lines.
This PR adds to the documentation of `on_bad_lines` for reading CSV files. Specifically, when using user-defined callables for `on_bad_lines` any bad line that isn't a 'line with too many fields' is silently skipped. The user should be aware of this behaviour.

The issue has been left open for further discussion of what is considered a 'bad line' and whether any code change should be made to accomodate the new definition of a bad line.

- [ ] closes #48020
- [ ] [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 [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.

friendly ping @mroeschke  @mroeschke  Thanks @kostyafarber 