Change namespace of DummyClientFace, Signal, Segmenter

refs #3940

Change-Id: I67ca0ecb8c916aab411a2f90454e0d25925978cd
diff --git a/tests/ping/server/ping-server.t.cpp b/tests/ping/server/ping-server.t.cpp
index b5c9948..05a7d84 100644
--- a/tests/ping/server/ping-server.t.cpp
+++ b/tests/ping/server/ping-server.t.cpp
@@ -1,6 +1,6 @@
 /* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
 /*
- * Copyright (c) 2014-2022,  Arizona Board of Regents.
+ * Copyright (c) 2014-2023,  Arizona Board of Regents.
  *
  * This file is part of ndn-tools (Named Data Networking Essential Tools).
  * See AUTHORS.md for complete list of ndn-tools authors and contributors.
@@ -59,7 +59,7 @@
   }
 
 protected:
-  util::DummyClientFace face{m_io, m_keyChain, {false, true}};
+  DummyClientFace face{m_io, m_keyChain, {false, true}};
   Options pingOptions{makeOptions()};
   PingServer pingServer{face, m_keyChain, pingOptions};
 };