Remove unused QObject parent arguments on options pages

In the new plugin setup scheme they are data members of the
plugin pimpl and never use the parent.

Change-Id: I28fe150393e8159064dcfbd113ce0320af50fd58
Reviewed-by: Eike Ziller <eike.ziller@qt.io>

src/plugins/todo/optionsdialog.cpp

@@ -34,8 +34,7 @@
 namespace Todo {
 namespace Internal {
 
-OptionsDialog::OptionsDialog(QWidget *parent) :
-    QWidget(parent),
+OptionsDialog::OptionsDialog() :
     ui(new Ui::OptionsDialog)
 {
     ui->setupUi(this);