Fix build on Boost 1.81 (espressomd#4655)

Description of changes:
- Replace file copy option that was deprecated in Boost 1.81

src/core/io/writer/h5md_core.cpp

@@ -56,10 +56,10 @@ static void backup_file(const std::string &from, const std::string &to) {
    * have gone wrong.
    */
   boost::filesystem::path pfrom(from), pto(to);
+  auto constexpr option_fail_if_exists = boost::filesystem::copy_options::none;
   try {
-    boost::filesystem::copy_file(
-        pfrom, pto, boost::filesystem::copy_option::fail_if_exists);
-  } catch (const boost::filesystem::filesystem_error &e) {
+    boost::filesystem::copy_file(pfrom, pto, option_fail_if_exists);
+  } catch (const boost::filesystem::filesystem_error &) {
     throw left_backupfile();
   }
 }