QmlJsEditor: Delay construction of QuickToolBar

It's now apparently created when the first .qml file opens.

Change-Id: I4bcd84d29da268565ee6e771f8c56c8b07ecdaf3
Reviewed-by: <github-actions-qt-creator@cristianadam.eu>
Reviewed-by: Eike Ziller <eike.ziller@qt.io>

src/plugins/qmljseditor/qmljseditor.cpp

@@ -116,7 +116,7 @@ void QmlJSEditorWidget::finalizeInitialization()
             this, &QmlJSEditorWidget::updateOutlineIndexNow);
 
     m_modelManager = ModelManagerInterface::instance();
-    m_contextPane = Internal::QmlJSEditorPlugin::quickToolBar();
+    m_contextPane = QuickToolBar::instance();
 
     m_modelManager->activateScan();