QQmlEngine: Fix documentation

The documentation should not recommend passing data via the context.
Rather, it should at least mention what a QQmlEngine actually is.

Pick-to: 6.6 6.5
Change-Id: Iee4faba7bb4e3bbbe385474badcb9781688f7147
Reviewed-by: Fabian Kosmale <fabian.kosmale@qt.io>
Reviewed-by: Sami Shalayel <sami.shalayel@qt.io>

src/qml/qml/qqmlengine.cpp

@@ -580,29 +580,16 @@ void QQmlEnginePrivate::init()
   \inmodule QtQml
   \brief The QQmlEngine class provides an environment for instantiating QML components.
 
-  Each QML component is instantiated in a QQmlContext.
-  QQmlContext's are essential for passing data to QML
-  components.  In QML, contexts are arranged hierarchically and this
-  hierarchy is managed by the QQmlEngine.
+  A QQmlEngine is used to manage \l{components}{QQmlComponent} and objects created from
+  them and execute their bindings and functions. QQmlEngine also inherits from
+  \l{QJSEngine} which allows seamless integration between your QML components and
+  JavaScript code.
 
-  Prior to creating any QML components, an application must have
-  created a QQmlEngine to gain access to a QML context.  The
-  following example shows how to create a simple Text item.
+  Each QML component is instantiated in a QQmlContext. In QML, contexts are arranged
+  hierarchically and this hierarchy is managed by the QQmlEngine. By default,
+  components are instantiated in the \l {QQmlEngine::rootContext()}{root context}.
 
-  \code
-  QQmlEngine engine;
-  QQmlComponent component(&engine);
-  component.setData("import QtQuick 2.0\nText { text: \"Hello world!\" }", QUrl());
-  QQuickItem *item = qobject_cast<QQuickItem *>(component.create());
-
-  //add item to view, etc
-  ...
-  \endcode
-
-  In this case, the Text item will be created in the engine's
-  \l {QQmlEngine::rootContext()}{root context}.
-
-  \sa QQmlComponent, QQmlContext, {QML Global Object}
+  \sa QQmlComponent, QQmlContext, {QML Global Object}, QQmlApplicationEngine
 */
 
 /*!