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/examples/plugin/main.cpp

@@ -1,31 +0,0 @@
-/*
-    SPDX-FileCopyrightText: 2024 Vlad Zahorodnii <vlad.zahorodnii@kde.org>
-
-    SPDX-License-Identifier: LGPL-2.0-or-later
-*/
-
-#include "eventlistener.h"
-
-#include <KPluginFactory>
-
-namespace KWin
-{
-
-class KWIN_EXPORT EventListenerFactory : public PluginFactory
-{
-    Q_OBJECT
-    Q_PLUGIN_METADATA(IID PluginFactory_iid FILE "metadata.json")
-    Q_INTERFACES(KWin::PluginFactory)
-
-public:
-    explicit EventListenerFactory() = default;
-
-    std::unique_ptr<Plugin> create() const override
-    {
-        return std::make_unique<EventListener>();
-    }
-};
-
-} // namespace KWin
-
-#include "main.moc"