unicode/norm: fix naming issue of example

Change-Id: I1cba68281c18adaf571e0dbdc4ad37698d313a5b
Reviewed-on: https://go-review.googlesource.com/38361
Run-TryBot: Marcel van Lohuizen <mpvl@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

unicode/norm/example_test.go

diff --git a/unicode/norm/example_test.go b/unicode/norm/example_test.go
index f2bec5b..8f3b156 100644
--- a/unicode/norm/example_test.go
+++ b/unicode/norm/example_test.go
@@ -10,7 +10,7 @@
 	"golang.org/x/text/unicode/norm"
 )
 
-func ExampleNextBoundary() {
+func ExampleForm_NextBoundary() {
 	s := norm.NFD.String("Mêlée")
 
 	for i := 0; i < len(s); {