Fashion is fickle. Tastes change. This is as true for food as it is for couture. In restaurants, tuna tartare gives way to house-made charcuterie, Italian flavors to Southern, then Asian, ones. Yesterday’s risotto is replaced by today’s grits — at least until grains like freekeh (roasted wheat) and quinoa begin to encroach. What’s in, out, and upcoming on Boston menus right now? Let’s take a look.