TWM references the since deprecated 'Matrix' class in two places: https://github.com/Pharophile/TilingWindowManager/blob/0f28620289443faf8d302001e40ae5ea6f1127f2/packages/TWM-Core/TWMHorizontalLayoutStrategy.class.st#L27 https://github.com/Pharophile/TilingWindowManager/blob/0f28620289443faf8d302001e40ae5ea6f1127f2/packages/TWM-Core/TWMVerticalLayoutStrategy.class.st#L27
