Doc: added names parameter in read_excel
closes #11468

Please Review.

Looks good, thanks!

You changed the explanation compared to the one included in `read_csv` (explicitly passing `header=None` when there is no header). This is indeed the current behaviour! (because for `read_excel` the default for `header` is 0, while for `read_csv` this is 'infer'). 
But, I think we should consider to make this more consistent. Will open a new issue for that.
