Fix deprecated warnings in qcustomplot

Author: gpospelov

thirdparty/qcustomplot/qcustomplot.cpp

@@ -678,8 +678,10 @@ QCPPaintBufferPixmap::~QCPPaintBufferPixmap()
 QCPPainter *QCPPaintBufferPixmap::startPainting()
 {
   QCPPainter *result = new QCPPainter(&mBuffer);
-#if QT_VERSION < QT_VERSION_CHECK(6, 0, 0)
-  result->setRenderHint(QPainter::HighQualityAntialiasing);
+#if QT_VERSION >= QT_VERSION_CHECK(5, 14, 0)
+  result->setRenderHint(QPainter::Antialiasing); // to make Antialiasing look good if using the OpenGL graphicssystem
+#else
+  result->setRenderHint(QPainter::HighQualityAntialiasing); // to make Antialiasing look good if using the OpenGL graphicssystem
 #endif
   return result;
 }
@@ -15488,7 +15490,9 @@ void QCustomPlot::paintEvent(QPaintEvent *event)
   QCPPainter painter(this);
   if (painter.isActive())
   {
-#if QT_VERSION < QT_VERSION_CHECK(6, 0, 0)
+#if QT_VERSION >= QT_VERSION_CHECK(5, 14, 0)
+  painter.setRenderHint(QPainter::Antialiasing); // to make Antialiasing look good if using the OpenGL graphicssystem
+#else
   painter.setRenderHint(QPainter::HighQualityAntialiasing); // to make Antialiasing look good if using the OpenGL graphicssystem
 #endif
     if (mBackgroundBrush.style() != Qt::NoBrush)