ENH: resample.sum documents a numeric_only argument

[rhshadrach]

https://pandas.pydata.org/docs/reference/api/pandas.core.resample.Resampler.sum.html

The parameters listed there include numeric_only though it is not in the function signature, and not implemented currently.

@mroeschke - is the right action here just to remove it from the docs?

[mroeschke]

Yes, I would say if the function doesn't accept this argument then numeric_only can just be removed from the docstring

[rhshadrach]

Similar to #46524, I think it'd be better to instead add numeric_only.