test: Return new_utxos from create_self_transfer_multi in MiniWallet

test/functional/feature_fee_estimation.py

@@ -52,7 +52,8 @@ def small_txpuzzle_randfee(
         raise RuntimeError(f"Insufficient funds: need {amount + fee}, have {total_in}")
     tx = wallet.create_self_transfer_multi(
         utxos_to_spend=utxos_to_spend,
-        fee_per_output=0)
+        fee_per_output=0,
+    )["tx"]
     tx.vout[0].nValue = int((total_in - amount - fee) * COIN)
     tx.vout.append(deepcopy(tx.vout[0]))
     tx.vout[1].nValue = int(amount * COIN)