Update integers.md

[kalyncoose]

Adds explanation to why an Example without an Output comment is useful for docs.

I was reading the Go blog article linked in this section and the official Go explanation of why an Example without an Output is still useful in some cases which I found particularly interesting and useful to add to this course's section. I think people would find this important as well since it gives the another use case as to why to use Testable Examples in their go docs.