build: switch to C++17

Change-Id: Id6217b5c993f3e4726e89773128b565e5f136bb6
diff --git a/tools/chunks/catchunks/pipeline-interests-cubic.hpp b/tools/chunks/catchunks/pipeline-interests-cubic.hpp
index daa59eb..87b4824 100644
--- a/tools/chunks/catchunks/pipeline-interests-cubic.hpp
+++ b/tools/chunks/catchunks/pipeline-interests-cubic.hpp
@@ -1,6 +1,6 @@
 /* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
 /*
- * Copyright (c) 2016-2021, Regents of the University of California,
+ * Copyright (c) 2016-2022, Regents of the University of California,
  *                          Colorado State University,
  *                          University Pierre & Marie Curie, Sorbonne University.
  *
@@ -28,8 +28,7 @@
 
 #include "pipeline-interests-adaptive.hpp"
 
-namespace ndn {
-namespace chunks {
+namespace ndn::chunks {
 
 /**
  * @brief Implements Cubic window increase and decrease.
@@ -55,7 +54,6 @@
   time::steady_clock::time_point m_lastDecrease; ///< time of last window decrease
 };
 
-} // namespace chunks
-} // namespace ndn
+} // namespace ndn::chunks
 
 #endif // NDN_TOOLS_CHUNKS_CATCHUNKS_PIPELINE_INTERESTS_CUBIC_HPP