qml6: fix geometry not being updated in qt6glitem
The QSGGeometryNode geometry used for rendering the qml6glsink will not resize until setGeometry is called with the updated geometry, QSGGeometry::updateTexturedRectGeometry by itself is seemingly not enough.
Before: 2024-04-13_22-24-56
After: 2024-04-13_22-25-31