cryptobyte: fix typo in test

Change-Id: I03178eca962c29ad03fd9b2fb57ad35c53c99860
GitHub-Last-Rev: 21a7a751920a5d3e650d1f91d17177f33e477ff1
GitHub-Pull-Request: golang/crypto#66
Reviewed-on: https://go-review.googlesource.com/c/151277
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

cryptobyte/cryptobyte_test.go

@@ -421,7 +421,7 @@ func TestFixedBuilderLengthPrefixed(t *testing.T) {
 		b.AddBytes(inner)
 	})
 	if got := b.BytesOrPanic(); len(got) != bufCap {
-		t.Errorf("Expected output lenght to be %d, got %d", bufCap, len(got))
+		t.Errorf("Expected output length to be %d, got %d", bufCap, len(got))
 	}
 }