Simplify Window::setDesktop()

workspace()->updateOnAllDesktopsOfTransients() is not needed because we
call setDesktops() for transients immediately after it.

src/window.cpp

@@ -1047,7 +1047,6 @@ void Window::setDesktops(QVector<VirtualDesktop *> desktops)
         return;
     }
 
-    const bool wasOnAllDesktops = isOnAllDesktops();
     m_desktops = desktops;
 
     if (windowManagementInterface()) {
@@ -1069,10 +1068,6 @@ void Window::setDesktops(QVector<VirtualDesktop *> desktops)
         }
     }
 
-    if (isOnAllDesktops() != wasOnAllDesktops) {
-        workspace()->updateOnAllDesktopsOfTransients(this);
-    }
-
     auto transients_stacking_order = workspace()->ensureStackingOrder(transients());
     for (auto it = transients_stacking_order.constBegin(); it != transients_stacking_order.constEnd(); ++it) {
         (*it)->setDesktops(desktops);