fix: untrack upstream KWin source (recipe-extracted, not Red Bear code)

Oracle found kwin_wayland_wrapper in tracked upstream KWin v6.3.4
source files. These are not Red Bear code — they are auto-extracted
by the recipe. Added to .gitignore per project policy.

local/recipes/kde/kwin/source/src/waylandshellintegration.cpp

@@ -1,19 +0,0 @@
-/*
-    SPDX-FileCopyrightText: 2020 Vlad Zahorodnii <vlad.zahorodnii@kde.org>
-
-    SPDX-License-Identifier: GPL-2.0-or-later
-*/
-
-#include "waylandshellintegration.h"
-
-namespace KWin
-{
-
-WaylandShellIntegration::WaylandShellIntegration(QObject *parent)
-    : QObject(parent)
-{
-}
-
-} // namespace KWin
-
-#include "moc_waylandshellintegration.cpp"