DOC: index and dropna docs missing from to_hdf docstring

[phofl]

Pandas version checks

• I have checked that the issue still exists on the latest versions of the docs on master here

Location of the documentation

https://pandas.pydata.org/docs/dev/reference/api/pandas.DataFrame.to_hdf.html?highlight=to_hdf#pandas.DataFrame.to_hdf

Documentation problem

• dropna
• index

are missing from the docstring

Suggested fix for documentation

Add them

[fanoway]

take

[pree-T]

May I work on this?

[phofl]

There is already a pr linked, but you can look for some other good first issue

[anirudhlakhotia]

I'd like to take a shot at this if it's still open