Update DataFrame.eq docstring
This was failing due to http://pandas.pydata.org/pandas-docs/version/0.24.0rc1/whatsnew/v0.24.0.html#dataframe-comparison-operations-broadcasting-changes

I'm surprised the doctests didn't catch this. @datapythonista, `pandas.DataFrame.eq` is included in the API docs at http://pandas-docs.github.io/pandas-docs-travis/api/generated/pandas.DataFrame.eq.html.  I believe it's because EX02 isn't passed in the code checks. @datapythonista do you know if that's deliberate?