Remove use of deprecated and now removed QueueBase::MaxPackets

Change-Id: I6aa6d2af4e6189ecd6bac774b2b846b18a0f9dd2
diff --git a/examples/ndn-simple.py b/examples/ndn-simple.py
index 108406a..7aeebce 100644
--- a/examples/ndn-simple.py
+++ b/examples/ndn-simple.py
@@ -47,7 +47,7 @@
 # Set default parameters for PointToPoint links and channels
 Config.SetDefault("ns3::PointToPointNetDevice::DataRate", StringValue("10Mbps"))
 Config.SetDefault("ns3::PointToPointChannel::Delay", StringValue("10ms"))
-Config::SetDefault("ns3::QueueBase::MaxPackets", UintegerValue(20))
+Config::SetDefault("ns3::QueueBase::MaxSize", StringValue("20p"))
 
 # Read optional command-line parameters (e.g., enable visualizer with ./waf --pyrun=<> --visualize
 import sys; cmd = CommandLine(); cmd.Parse(sys.argv);