Tweak reverse examples

[sogaiu]

This PR suggests tweaking some of the examples for reverse.

The return value for the second example did not match recent behavior for janet so this was updated.

The third example was removed because the current docstring does not specify a behavior for operating on keywords:

Reverses the order of the elements in a given array or tuple and returns a new array. If a string or buffer is provided, returns a buffer instead.