scrypt: update example to match recommendation two lines below

Change-Id: I6eb5db30df9bc1c4b3c4124c9cdd3d504d33ad9d
GitHub-Last-Rev: 1f585c4bf946a3241f8c38e1e954c4e5f8dc4713
GitHub-Pull-Request: golang/crypto#43
Reviewed-on: https://go-review.googlesource.com/110120
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

scrypt/scrypt.go

@@ -218,7 +218,7 @@ func smix(b []byte, r, N int, v, xy []uint32) {
 // For example, you can get a derived key for e.g. AES-256 (which needs a
 // 32-byte key) by doing:
 //
-//      dk, err := scrypt.Key([]byte("some password"), salt, 16384, 8, 1, 32)
+//      dk, err := scrypt.Key([]byte("some password"), salt, 32768, 8, 1, 32)
 //
 // The recommended parameters for interactive logins as of 2017 are N=32768, r=8
 // and p=1. The parameters N, r, and p should be increased as memory latency and