Avoid deprecated ndn-cxx functions

Change-Id: I5d9ac045740267db783ff724c938b659b49c40ee
diff --git a/tests/peek/ndnpeek.t.cpp b/tests/peek/ndnpeek.t.cpp
index 336b1de..dfb8768 100644
--- a/tests/peek/ndnpeek.t.cpp
+++ b/tests/peek/ndnpeek.t.cpp
@@ -143,8 +143,7 @@
   initialize(options);
 
   auto data = makeData(options.name);
-  const std::string payload = "NdnPeekTest";
-  data->setContent(reinterpret_cast<const uint8_t*>(payload.data()), payload.size());
+  data->setContent({'n', 'd', 'n', 'p', 'e', 'e', 'k'});
 
   {
     CoutRedirector redir(output);
@@ -177,8 +176,7 @@
 
   auto data = makeData(Name(options.name).append("suffix"));
   data->setFreshnessPeriod(1_s);
-  const std::string payload = "NdnPeekTest";
-  data->setContent(reinterpret_cast<const uint8_t*>(payload.data()), payload.size());
+  data->setContent({'n', 'd', 'n', 'p', 'e', 'e', 'k'});
 
   {
     CoutRedirector redir(output);