blog: update one example in "Laws of Reflection"

A recent change to fmt that has it print reflect.Values nicer
invalidates the pedagogical value of one example. Tweak the
example.

Change-Id: I9ca7f81957832b26c47270d8967b7aeef801b1a8
Reviewed-on: https://go-review.googlesource.com/39530
Reviewed-by: Ian Lance Taylor <iant@golang.org>
1 file changed