Limit send_quantum to 30xMSS

quiche/src/recovery/bbr/per_ack.rs

diff --git a/quiche/src/recovery/bbr/per_ack.rs b/quiche/src/recovery/bbr/per_ack.rs
index 6fe5651..6c85fc2 100644
--- a/quiche/src/recovery/bbr/per_ack.rs
+++ b/quiche/src/recovery/bbr/per_ack.rs
@@ -123,7 +123,7 @@
 
         rate if rate < PACING_RATE_24MBPS => 2 * r.max_datagram_size,
 
-        _ => cmp::min((rate / 1000_u64) as usize, 64 * 1024),
+        _ => cmp::min((rate / 1000_u64) as usize, 30 * r.max_datagram_size),
     }
 }