interest: remove deprecated setDefaultCanBePrefix()

Change-Id: Ifaffb7cc7772a31c3b396c60b816e783d70b7041
diff --git a/tests/unit/security/certificate-fetcher-from-network.t.cpp b/tests/unit/security/certificate-fetcher-from-network.t.cpp
index 36a1ae9..29d8243 100644
--- a/tests/unit/security/certificate-fetcher-from-network.t.cpp
+++ b/tests/unit/security/certificate-fetcher-from-network.t.cpp
@@ -1,6 +1,6 @@
 /* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
 /*
- * Copyright (c) 2013-2021 Regents of the University of California.
+ * Copyright (c) 2013-2022 Regents of the University of California.
  *
  * This file is part of ndn-cxx library (NDN C++ library with eXperimental eXtensions).
  *
@@ -62,7 +62,6 @@
     cache.insert(subSubIdentity.getDefaultKey().getDefaultCertificate());
 
     m_keyChain.sign(data, signingByIdentity(subSubIdentity));
-    interest.setCanBePrefix(false);
     m_keyChain.sign(interest, signingByIdentity(subSubIdentity));
 
     processInterest = [this] (const Interest& i) { makeResponse(i); };