PR #32068 follow up - Print merged df result in doc
- [x] follow up to PR #32068 which closed #12550  - small fix - see https://github.com/pandas-dev/pandas/pull/32068#discussion_r386029773


@simonjayhawkins  just made the change and rendered it locally.

![Screenshot 2020-02-29 at 15 15 08](https://user-images.githubusercontent.com/16509490/75610178-b7372f80-5b06-11ea-85dd-50c2aafa081c.png)
 Thanks @ryankarlos 