Follow kwindoweffects::windowSizes deprecation

src/plugins/windowsystem/windoweffects.cpp

@@ -67,11 +67,13 @@ void WindowEffects::slideWindow(WId id, KWindowEffects::SlideFromLocation locati
     w->setProperty("kwin_slide_offset", offset);
 }
 
+#if KWINDOWSYSTEM_BUILD_DEPRECATED_SINCE(5, 81)
 QList<QSize> WindowEffects::windowSizes(const QList<WId> &ids)
 {
     Q_UNUSED(ids)
     return {};
 }
+#endif
 
 void WindowEffects::presentWindows(WId controller, const QList<WId> &ids)
 {

src/plugins/windowsystem/windoweffects.h

@@ -18,7 +18,9 @@ public:
 
     bool isEffectAvailable(KWindowEffects::Effect effect) override;
     void slideWindow(WId id, KWindowEffects::SlideFromLocation location, int offset) override;
+#if KWINDOWSYSTEM_BUILD_DEPRECATED_SINCE(5, 81)
     QList<QSize> windowSizes(const QList<WId> &ids) override;
+#endif
     void presentWindows(WId controller, const QList<WId> &ids) override;
     void presentWindows(WId controller, int desktop = NET::OnAllDesktops) override;
     void highlightWindows(WId controller, const QList<WId> &ids) override;