Remove getPaginator() from PaginatorInterface

What is the need and the output of the method ```PaginatorInterface::getPaginator()```? I couldn't find any use or tests for this method. But I have to declare it in my Paginator? Why should a Paginator return itself?

There might be a need for this method in [IlluminatePaginatorAdapter](https://github.com/thephpleague/fractal/blob/master/src/Pagination/IlluminatePaginatorAdapter.php#L98), but not in the Interface.