DOC: added index, dropna description for HDF methods #45030
- [ ] closes #45030
- [ ] [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 an entry in the latest `doc/source/whatsnew/vX.X.X.rst` file if fixing a bug or adding a new feature.

thanks @alexondor  Hello @jreback ! Could you please explain about failed test "pandas.Series.to_hdf:Wrong parameters order"? Is it correct?  I inserted comments in order to function input parameters. But there was previously violated order.