doc/effective_go.html: Add missing '...' for fmt.Sprintf()
doc/effective_go.html: Add missing '...' for fmt.Sprintf()

The '...' was missing on a call to fmt.Sprintf() which would result in
the slice being printed instead of the correct result.

R=golang-dev, gri
CC=golang-dev
http://codereview.appspot.com/5967051

Committer: Robert Griesemer <a6752097faebf1f02d80107d77a9be009089afe3@golang.org>

h8liu/golang,h8liu/golang,h8liu/golang,h8liu/golang,h8liu/golang,h8liu/golang,h8liu/golang