sha3: fix TestAppend to loop twice, to match the comments.

Change-Id: I84713a4173d9de4cd3d14991b8a47c9fbae7dcfd
Reviewed-on: https://go-review.googlesource.com/8976
Reviewed-by: David Symonds <dsymonds@golang.org>

sha3/sha3_test.go

@@ -159,7 +159,7 @@ func TestAppend(t *testing.T) {
 	testUnalignedAndGeneric(t, func(impl string) {
 		d := New224()
 
-		for capacity := 2; capacity < 64; capacity += 64 {
+		for capacity := 2; capacity <= 66; capacity += 64 {
 			// The first time around the loop, Sum will have to reallocate.
 			// The second time, it will not.
 			buf := make([]byte, 2, capacity)