Switch to std::filesystem

Change-Id: Idd88815c8971a1dd6a592ac9d3f46d5925afd21b
diff --git a/tests/key-chain-fixture.cpp b/tests/key-chain-fixture.cpp
index f29153f..bae6ca7 100644
--- a/tests/key-chain-fixture.cpp
+++ b/tests/key-chain-fixture.cpp
@@ -27,7 +27,8 @@
 
 #include <ndn-cxx/util/io.hpp>
 
-#include <boost/filesystem/operations.hpp>
+#include <filesystem>
+#include <system_error>
 
 namespace nlsr::tests {
 
@@ -40,9 +41,9 @@
 
 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
   }
 }