lnd_test: bump async bidrect timeout to account sphinx replay writes

lnd_test.go

@@ -5006,7 +5006,7 @@ func testBidirectionalAsyncPayments(net *lntest.NetworkHarness, t *harnessTest)
 
 	// Wait for Alice and Bob receive their payments, and throw and error
 	// if something goes wrong.
-	maxTime := 20 * time.Second
+	maxTime := 60 * time.Second
 	for i := 0; i < 2; i++ {
 		select {
 		case err := <-errChan: