Fix `series.str.startswith(tuple)`
- [x] closes #48575 and #38281
- [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.
- [ ] Added an entry in the latest `doc/source/whatsnew/vX.X.X.rst` file if fixing a bug or adding a new feature.

Should I add a note in `doc/source/whatsnew/v1.5.0.rst`?
> Could you also add a tuple input example in the `Examples` section of the docstrings?

Certainly. Thanks for the quick fix @janosh!  @mroeschke You may want to close #38281 manually. I forgot to put a 'closes' in front of its PR number above.