Update poll and encrypted messaging membership fixtures

tests/test_dm_groups.c

@@ -63,7 +63,7 @@ static void seed_channel(void) {
         uint8_t body[112], join[64], tree[64];
         assert(member_sync_build_join_msg(x, ed, nodes[author]->node_id, nodes[author]->my_keys.public_key, 1, body, sizeof(body)) == 112);
         assert(sc_ed25519_sign(nodes[author]->my_ed25519_privkey, body, sizeof(body), join) == SC_OK);
-        assert(!member_sync_sign_pubkey(priv, nodes[author]->my_keys.public_key, tree));
+        assert(!member_sync_sign_join(priv, join, tree));
         assert(member_sync_put(nodes[dst], channel, nodes[author]->node_id, nodes[author]->my_keys.public_key,
             nodes[author]->my_ed25519_pubkey, join, 1, NULL, 0, "{}", NULL, NULL, 0, 0, tree) >= 0);
     }