Migrate to ndn-cxx 0.7.1: Part 1

Change-Id: I621a6230272cfde5d84aa5ca9abdf40a91337491
diff --git a/tests/unit-tests/challenge-credential.t.cpp b/tests/unit-tests/challenge-credential.t.cpp
index 236d274..46c5928 100644
--- a/tests/unit-tests/challenge-credential.t.cpp
+++ b/tests/unit-tests/challenge-credential.t.cpp
@@ -61,7 +61,7 @@
   auto identityB = addIdentity(Name("/trust/cert"));
   auto keyB = identityB.getDefaultKey();
   auto credentialName = Name(keyB.getName()).append("Credential").appendVersion();
-  security::v2::Certificate credential;
+  security::Certificate credential;
   credential.setName(credentialName);
   credential.setContent(keyB.getPublicKey().data(), keyB.getPublicKey().size());
   SignatureInfo signatureInfo;