refactor: Use C++20 std::chrono::days

src/qt/guiutil.cpp

@@ -723,8 +723,7 @@ QString ConnectionTypeToQString(ConnectionType conn_type, bool prepend_direction
 
 QString formatDurationStr(std::chrono::seconds dur)
 {
-    using days = std::chrono::duration<int, std::ratio<86400>>; // can remove this line after C++20
-    const auto d{std::chrono::duration_cast<days>(dur)};
+    const auto d{std::chrono::duration_cast<std::chrono::days>(dur)};
     const auto h{std::chrono::duration_cast<std::chrono::hours>(dur - d)};
     const auto m{std::chrono::duration_cast<std::chrono::minutes>(dur - d - h)};
     const auto s{std::chrono::duration_cast<std::chrono::seconds>(dur - d - h - m)};