Switch to std::filesystem

Change-Id: If70258048d6f54c3e9f0a25bf8f3e327411c42ac
diff --git a/tests/identity-management-fixture.cpp b/tests/identity-management-fixture.cpp
index ef5ab5c..106797b 100644
--- a/tests/identity-management-fixture.cpp
+++ b/tests/identity-management-fixture.cpp
@@ -1,6 +1,6 @@
 /* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
 /*
- * Copyright (c) 2014-2022, Regents of the University of California.
+ * Copyright (c) 2014-2024, Regents of the University of California.
  *
  * This file is part of NDN repo-ng (Next generation of NDN repository).
  * See AUTHORS.md for complete list of repo-ng authors and contributors.
@@ -25,7 +25,7 @@
 #include <ndn-cxx/security/certificate.hpp>
 #include <ndn-cxx/util/io.hpp>
 
-#include <boost/filesystem.hpp>
+#include <filesystem>
 
 namespace repo::tests {
 
@@ -37,9 +37,9 @@
 
 IdentityManagementFixture::~IdentityManagementFixture()
 {
-  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
   }
 }