Editors: Remove useless parent widget argument from create/duplicate

It was never called with a sensible value anyhow, and only complicates things.

Change-Id: I005848700b6c00114d91495670d4a0e15a2d2e64
Reviewed-by: Eike Ziller <eike.ziller@digia.com>

src/plugins/texteditor/plaintexteditorfactory.h

@@ -45,7 +45,7 @@ public:
     PlainTextEditorFactory(QObject *parent = 0);
 
     using Core::IEditorFactory::addMimeType;
-    Core::IEditor *createEditor(QWidget *parent);
+    Core::IEditor *createEditor();
 
 private slots:
     void updateEditorInfoBar(Core::IEditor *editor);