unicode/norm: use io.SeekCurrent constant in tests

Change-Id: I8a8b90b54baa0f8a3742e39b64c57f8af570e62d
Reviewed-on: https://go-review.googlesource.com/105737
Run-TryBot: Tobias Klauser <tobias.klauser@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
diff --git a/unicode/norm/example_iter_test.go b/unicode/norm/example_iter_test.go
index 82df89c..998d896 100644
--- a/unicode/norm/example_iter_test.go
+++ b/unicode/norm/example_iter_test.go
@@ -7,6 +7,7 @@
 import (
 	"bytes"
 	"fmt"
+	"io"
 	"unicode/utf8"
 
 	"golang.org/x/text/unicode/norm"
@@ -48,8 +49,8 @@
 			return false
 		}
 		if n := int64(FindPrefix(a[ia.Pos():], b[ib.Pos():])); n != 0 {
-			ia.Seek(n, 1)
-			ib.Seek(n, 1)
+			ia.Seek(n, io.SeekCurrent)
+			ib.Seek(n, io.SeekCurrent)
 		}
 	}
 	return ia.Done() && ib.Done()