apps: Fixing typo in ns3::ndn::Producer

Change-Id: Id66b7c4b93ddd95d90d2137a2e5e315ae8e79ca2
Refs: #2731
diff --git a/apps/ndn-producer.cpp b/apps/ndn-producer.cpp
index c61dd8f..a1a63ab 100644
--- a/apps/ndn-producer.cpp
+++ b/apps/ndn-producer.cpp
@@ -124,7 +124,7 @@
 
   data->setSignature(signature);
 
-  NS_LOG_INFO("node(" << GetNode()->GetId() << ") respodning with Data: " << data->getName());
+  NS_LOG_INFO("node(" << GetNode()->GetId() << ") responding with Data: " << data->getName());
 
   // to create real wire encoding
   data->wireEncode();