Switch to std::filesystem

Drop the dependency on Boost.Filesystem

Change-Id: I5d6f6fe38cd0cf1c6996221188fa63db146dc9f9
diff --git a/tests/key-chain-fixture.cpp b/tests/key-chain-fixture.cpp
index fefc7cf..9c5c17a 100644
--- a/tests/key-chain-fixture.cpp
+++ b/tests/key-chain-fixture.cpp
@@ -1,6 +1,6 @@
 /* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
 /*
- * Copyright (c) 2013-2023 Regents of the University of California.
+ * Copyright (c) 2013-2024 Regents of the University of California.
  *
  * This file is part of ndn-cxx library (NDN C++ library with eXperimental eXtensions).
  *
@@ -23,7 +23,8 @@
 
 #include "ndn-cxx/util/io.hpp"
 
-#include <boost/filesystem/operations.hpp>
+#include <filesystem>
+#include <system_error>
 
 namespace ndn::tests {
 
@@ -36,9 +37,9 @@
 
 KeyChainFixture::~KeyChainFixture()
 {
-  boost::system::error_code ec;
+  std::error_code ec;
   for (const auto& certFile : m_certFiles) {
-    boost::filesystem::remove(certFile, ec); // ignore error
+    std::filesystem::remove(certFile, ec); // ignore error
   }
 }