build: switch to C++17

Change-Id: I92039300ce845de0312dceccb94c128229ed60c4
diff --git a/tests/unit/security/pib/pib-data-fixture.hpp b/tests/unit/security/pib/pib-data-fixture.hpp
index 66e7fbf..64c8652 100644
--- a/tests/unit/security/pib/pib-data-fixture.hpp
+++ b/tests/unit/security/pib/pib-data-fixture.hpp
@@ -1,6 +1,6 @@
 /* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
 /*
- * Copyright (c) 2013-2022 Regents of the University of California.
+ * Copyright (c) 2013-2023 Regents of the University of California.
  *
  * This file is part of ndn-cxx library (NDN C++ library with eXperimental eXtensions).
  *
@@ -35,10 +35,10 @@
 public:
   PibDataFixture();
 
-  NDN_CXX_NODISCARD static shared_ptr<PibImpl>
+  [[nodiscard]] static shared_ptr<PibImpl>
   makePibWithIdentity(const Name& idName);
 
-  NDN_CXX_NODISCARD static shared_ptr<PibImpl>
+  [[nodiscard]] static shared_ptr<PibImpl>
   makePibWithKey(const Name& keyName, span<const uint8_t> key);
 
 public: