Interesting question. First I'd say veganism isn't a monolith, so opinions will probably differ on the matter. For instance, there is some debate about whether figs are vegan since they are pollinated by fig wasps which then die inside (but are completely absorbed by the fig). I think galls fall into a similar space, but perhaps are less of an issue since they are nominally rid of the insects once they are harvested (though I somehow doubt it can be guaranteed to be completely larvae-free).