bb-reorder: Remove a misfiring micro-optimization (PR96475)
When the compgotos pass copies the tail of blocks ending in an indirect
jump, there is a micro-optimization to not copy the last one, since the
original block will then just be deleted. This does not work properly
if cleanup_cfg does not merge all pairs of blocks we expect it to. It
also does not work if that last block can be merged into multiple
predecessors.