Deflaky Bbr2DefaultTopologyTest.SimpleTransfer2RTTAggregationBytes by increase the margin on smoothed rtt.

PiperOrigin-RevId: 340924278
Change-Id: I93e000504946b082196fe8afcda1db8bdf11b4e9
diff --git a/quic/core/congestion_control/bbr2_simulator_test.cc b/quic/core/congestion_control/bbr2_simulator_test.cc
index 9ef68dd..f446ab5 100644
--- a/quic/core/congestion_control/bbr2_simulator_test.cc
+++ b/quic/core/congestion_control/bbr2_simulator_test.cc
@@ -474,9 +474,9 @@
                    sender_->ExportDebugState().bandwidth_hi, 0.01f);
 
   EXPECT_LE(sender_loss_rate_in_packets(), 0.05);
-  // The margin here is high, because the aggregation greatly increases
-  // smoothed rtt.
-  EXPECT_GE(params.RTT() * 4, rtt_stats()->smoothed_rtt());
+  // The margin here is high, because both link level aggregation and ack
+  // decimation can greatly increase smoothed rtt.
+  EXPECT_GE(params.RTT() * 5, rtt_stats()->smoothed_rtt());
   EXPECT_APPROX_EQ(params.RTT(), rtt_stats()->min_rtt(), 0.2f);
 }