DOC: unclear kwarg null_counts
#### Location of the documentation

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

#### Documentation problem

Keyword ``null_counts`` from its name may be considered as a need to count null items.
However, the documentation explains that is quite the opposite - count **non-null** items.
I suggest to rename it with ``show_counts`` and maintain the old behavior.

#### Suggested fix for documentation

Replace ``null_counts`` with ``show_counts``.
It will make it more clear what this kwarg means without even the need to read docs.

#### API

It the suggested rename is implemented, then need to start deprecation of kwarg ``null_counts``.