QmlDesigner: Remove superfluous deleteLater calls

All those QObjects are part of the parent child hierarchy
and do not have to be deleted manually.
This slicences two QCoreApplication::postEvent: Unexpected null receiver,
because the graphics scene is now created lazily.

Change-Id: Ibfe4aaed2173f591e90186b570f8c8bb9e708494
Reviewed-by: Tim Jenssen <tim.jenssen@qt.io>

src/plugins/qmldesigner/components/formeditor/formeditorview.cpp

@@ -65,11 +65,6 @@ FormEditorView::~FormEditorView()
 {
     m_currentTool = 0;
     qDeleteAll(m_customToolList);
-
-    // delete scene after tools to prevent access to the scene while
-    // calling destructors (and also double deletion of items)
-    m_scene->deleteLater();
-    m_formEditorWidget->deleteLater();
 }
 
 void FormEditorView::modelAttached(Model *model)

src/plugins/qmldesigner/components/texteditor/texteditorview.cpp

@@ -63,7 +63,6 @@ TextEditorView::TextEditorView(QObject *parent)
 
 TextEditorView::~TextEditorView()
 {
-    m_widget->deleteLater();
 }
 
 void TextEditorView::modelAttached(Model *model)