Avoid deprecated ndn-cxx functions

Change-Id: Ib9220786a724327b89dcc328c8f34a5c8fe1fdd9
diff --git a/tests/key-chain-fixture.cpp b/tests/key-chain-fixture.cpp
index c374fa3..c1abcf8 100644
--- a/tests/key-chain-fixture.cpp
+++ b/tests/key-chain-fixture.cpp
@@ -1,6 +1,6 @@
 /* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
 /*
- * Copyright (c) 2013-2020 Regents of the University of California.
+ * Copyright (c) 2013-2022 Regents of the University of California.
  *
  * This file is part of NDNS (Named Data Networking Domain Name Service).
  * See AUTHORS.md for complete list of NDNS authors and contributors.
@@ -55,7 +55,7 @@
   cert.setFreshnessPeriod(1_h);
 
   // set content
-  cert.setContent(key.getPublicKey().data(), key.getPublicKey().size());
+  cert.setContent(key.getPublicKey());
 
   // set signature info
   ndn::SignatureInfo info;