test: fix TestTransactionTimeoutSecondStatement by increasing timeout

Problem:
The test is flaky in CI because the local transaction_timeout(20ms) is too tight to complete the update operation, leading to a `context deadline exceeded` error or `spanner: code = "DeadlineExceeded"...` error.

Solution:
By running the test 10,000 times with the -race flag, I found that only setting transaction_timeout to at least 1s passees 10,000 times. I have experimented with 0.06s, 0.2s, and 0.5s. However, all of them (0.06s, 0.2s, and 0.5s) fail before passing 10,000 times.

Signed-off-by: Yong-Han Chen <hank96015@gmail.com>

Author: HankStat

transaction_test.go

@@ -323,14 +323,14 @@ func TestTransactionTimeoutSecondStatement(t *testing.T) {
 	ctx := context.Background()
 
 	tx, _ := db.BeginTx(ctx, &sql.TxOptions{})
-	if _, err := tx.ExecContext(ctx, "set local transaction_timeout=20ms"); err != nil {
+	if _, err := tx.ExecContext(ctx, "set local transaction_timeout=1000ms"); err != nil {
 		t.Fatal(err)
 	}
 	if _, err := tx.ExecContext(ctx, testutil.UpdateBarSetFoo); err != nil {
 		t.Fatal(err)
 	}
 
-	server.TestSpanner.PutExecutionTime(testutil.MethodExecuteStreamingSql, testutil.SimulatedExecutionTime{MinimumExecutionTime: 50 * time.Millisecond})
+	server.TestSpanner.PutExecutionTime(testutil.MethodExecuteStreamingSql, testutil.SimulatedExecutionTime{MinimumExecutionTime: 1500 * time.Millisecond})
 	rows, err := tx.QueryContext(ctx, testutil.SelectFooFromBar, ExecOptions{DirectExecuteQuery: true})
 	if rows != nil {
 		_ = rows.Close()