KSelectionProxyModelTest: Skip tests broken by upstream changes
Four affected test rows: * A-1-SubTrees-0-06 * A-1-Children-0-06 * A-0-SubTrees-0-06 * A-0-Children-0-06 These tests hasn't changed for ages. But upstream model code did. Once the following patches are released and reach our CI's minimum target version, we can revert this skip: * https://codereview.qt-project.org/c/qt/qtbase/+/487372 * https://codereview.qt-project.org/c/qt/qtbase/+/487503