Revert "scene: Add an assert to debug crash in BlurEffect::prePaintWindow()"
This reverts commit b708a93c.
The crashes in BlurEffect::prePaintWindow() continue occurring without tripping this code, so the culprit must lie elsewhere.
(cherry picked from commit 0f78a272)
Co-authored-by: Vlad Zahorodnii vlad.zahorodnii@kde.org