fn align_serif_edge(axis: &mut Axis, base_edge_ix: usize, serif_edge_ix: usize)
Shift the serif edge by the adjustment made to base edge.
See https://gitlab.freedesktop.org/freetype/freetype/-/blob/57617782464411201ce7bbc93b086c1b4d7d84a5/src/autofit/aflatin.c#L2975