Mentions make, len being overloaded with no example of len overload

[nzhenry]

In the 'Slices' section, the comment: 'you'll note that make and len are overloaded' is backed up by two examples of usage of make with different numbers of arguments, but no equivalent examples of len usage.

[karlseguin]

My only thought is to take that entire paragraph and stick it the end of the section, before we start talking about maps. At this point, both make and len have been seen. Thoughts?