refactor: drop swapItemsAt conditional compile

since Qt 5.15 needed

Author: CoelacanthusHex

makespec/BUILDVERSION

@@ -1 +1 @@
-123
+124

src/base/settings.cpp

@@ -16,10 +16,6 @@
 //
 #define LEMON_MODULE_NAME "Setting"
 
-#if QT_VERSION < QT_VERSION_CHECK(5, 13, 0)
-#define swapItemsAt swap
-#endif
-
 #if QT_VERSION >= QT_VERSION_CHECK(5, 14, 0)
 #define QT_SkipEmptyParts Qt::SkipEmptyParts
 #else

src/core/contest.cpp

@@ -20,10 +20,6 @@
 #include <QMessageBox>
 #include <utility>
 
-#if QT_VERSION < QT_VERSION_CHECK(5, 13, 0)
-#define swapItemsAt swap
-#endif
-
 Contest::Contest(QObject *parent) : QObject(parent) {}
 
 void Contest::setSettings(Settings *_settings) { settings = _settings; }

src/core/contestant.cpp

@@ -12,10 +12,6 @@
 #include "core/contest.h"
 #include <utility>
 
-#if QT_VERSION < QT_VERSION_CHECK(5, 13, 0)
-#define swapItemsAt swap
-#endif
-
 Contestant::Contestant(QObject *parent) : QObject(parent) {}
 
 auto Contestant::getContestantName() const -> const QString & { return contestantName; }