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/designer/settingspage.cpp

@@ -66,8 +66,7 @@ void SettingsPage::finish()
     delete m_widget;
 }
 
-SettingsPageProvider::SettingsPageProvider(QObject *parent)
-    : IOptionsPageProvider(parent)
+SettingsPageProvider::SettingsPageProvider()
 {
     setCategory(Designer::Constants::SETTINGS_CATEGORY);
     setDisplayCategory(QCoreApplication::translate("Designer",