fix(spanner): update staleness bound (#10118)

diff --git a/spanner/integration_test.go b/spanner/integration_test.go
index 99388e7..d701fa3 100644
--- a/spanner/integration_test.go
+++ b/spanner/integration_test.go
@@ -623,7 +623,7 @@
 		{
 			name: "max_staleness",
 			want: [][]interface{}{{int64(1), "Marc", "Foo"}, {int64(3), "Alpha", "Beta"}, {int64(4), "Last", "End"}},
-			tb:   MaxStaleness(time.Second),
+			tb:   MaxStaleness(time.Nanosecond),
 			checkTs: func(ts time.Time) error {
 				if ts.Before(writes[3].ts) {
 					return fmt.Errorf("read got timestamp %v, want it to be no earlier than %v", ts, writes[3].ts)