client: Fix window margin calculation

Don't subtract the size of the window frame margin from the content
area. Fixes an issue where an area of the window is unclickable when
client-side decorations are in use.

Fixes: QTBUG-120392
Pick-to: 6.7 6.6 6.5
Change-Id: I6a89b2d463be084233ea3448cacfbbd09d66b96e
Reviewed-by: David Edmundson <davidedmundson@kde.org>
Reviewed-by: Kai Uwe Broulik <kde@privat.broulik.de>

src/plugins/platforms/wayland/qwaylandwindow.cpp

@@ -1350,8 +1350,8 @@ void QWaylandWindow::handleMouseEventWithDecoration(QWaylandInputDevice *inputDe
     QMargins marg = frameMargins();
     QRect windowRect(0 + marg.left(),
                      0 + marg.top(),
-                     geometry().size().width() - marg.right(),
-                     geometry().size().height() - marg.bottom());
+                     geometry().size().width(),
+                     geometry().size().height());
     if (windowRect.contains(e.local.toPoint()) || mMousePressedInContentArea != Qt::NoButton) {
         const QPointF localTranslated = mapFromWlSurface(e.local);
         QPointF globalTranslated = e.global;