Drop Qt5: Qml lib / QmlDesigner: Get rid of QOverload

Add a context object into some lambdas.

Change-Id: I16ee7a0c061483e4d90c9e015852c41a4f3cde90
Reviewed-by: Tim Jenssen <tim.jenssen@qt.io>
Reviewed-by: <github-actions-qt-creator@cristianadam.eu>

src/plugins/qmlprojectmanager/qmlmainfileaspect.cpp

@@ -85,8 +85,7 @@ void QmlMainFileAspect::addToLayout(LayoutBuilder &builder)
 
     connect(ProjectExplorerPlugin::instance(), &ProjectExplorerPlugin::fileListChanged,
             this, &QmlMainFileAspect::updateFileComboBox);
-    connect(m_fileListCombo, QOverload<int>::of(&QComboBox::activated),
-            this, &QmlMainFileAspect::setMainScript);
+    connect(m_fileListCombo, &QComboBox::activated, this, &QmlMainFileAspect::setMainScript);
 
     builder.addItems({tr("Main QML file:"), m_fileListCombo.data()});
 }