Remove use of deprecated and now removed QueueBase::MaxPackets

Change-Id: I6aa6d2af4e6189ecd6bac774b2b846b18a0f9dd2
diff --git a/tests/unit-tests/ndn-cxx/face.t.cpp b/tests/unit-tests/ndn-cxx/face.t.cpp
index df84a30..f062728 100644
--- a/tests/unit-tests/ndn-cxx/face.t.cpp
+++ b/tests/unit-tests/ndn-cxx/face.t.cpp
@@ -38,7 +38,7 @@
   {
     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"));
 
     createTopology({{"A", "B"}});
     addRoutes({{"A", "B", "/test", 1}});