A mistake in the `chunk` function example comments

[zhangfelix]

The return of the example in chunk function is [[1,2],[3,4],[5]], rather than [[1,2],[3,4],5].

Current example:

chunk([1, 2, 3, 4, 5], 2) # [[1,2],[3,4],5]

It should be:

chunk([1, 2, 3, 4, 5], 2) # [[1,2],[3,4],[5]]