Windows Vista Style: Draw dock widget title with Qt::TextShowMnemonic

Align with the other styles.

Task-number: QTBUG-54485
Change-Id: Ic8d008c59f5acf858b8ba6fbea5dd30b8aa9634c
Reviewed-by: Andy Shaw <andy.shaw@qt.io>

src/plugins/styles/windowsvista/qwindowsvistastyle.cpp

@@ -1430,7 +1430,8 @@ void QWindowsVistaStyle::drawControl(ControlElement element, const QStyleOption
                                                                       verticalTitleBar ? titleRect.height() : titleRect.width());
                 const int indent = 4;
                 drawItemText(painter, rect.adjusted(indent + 1, 1, -indent - 1, -1),
-                                Qt::AlignLeft | Qt::AlignVCenter, dwOpt->palette,
+                                Qt::AlignLeft | Qt::AlignVCenter | Qt::TextShowMnemonic,
+                                dwOpt->palette,
                                 dwOpt->state & State_Enabled, titleText,
                                 QPalette::WindowText);
                 }