DolphinQt: Remove redundant window hints

Remove window hints clearing the flag Qt::WindowContextHelpButtonHint,
which is already off by default in Qt 6.

In Qt 5 this flag was set by default for QDialogs, and on Windows put a
? button in the corner of the title bar allowing users to activate Qt's
QWhatsThis help system for a given widget. Since we don't set that text
the ? button was useless and so we hid it manually.

Source/Core/DolphinQt/ConvertDialog.cpp

@@ -42,7 +42,6 @@ ConvertDialog::ConvertDialog(QList<std::shared_ptr<const UICommon::GameFile>> fi
   ASSERT(!m_files.empty());
 
   setWindowTitle(tr("Convert"));
-  setWindowFlags(windowFlags() & ~Qt::WindowContextHelpButtonHint);
 
   QGridLayout* grid_layout = new QGridLayout;
   grid_layout->setColumnStretch(1, 1);