test: Don't rely on incentive incompatible replacement in mempool_accept_v3.py

Author: sdaftuar

test/functional/mempool_accept_v3.py

@@ -533,10 +533,10 @@ def test_v3_sibling_eviction(self):
         tx_unrelated_replacee = self.wallet.send_self_transfer(from_node=node, utxo_to_spend=utxo_unrelated_conflict)
         assert tx_unrelated_replacee["txid"] in node.getrawmempool()
 
-        fee_to_beat_child2 = int(tx_v3_child_2["fee"] * COIN)
+        fee_to_beat = max(int(tx_v3_child_2["fee"] * COIN), int(tx_unrelated_replacee["fee"]*COIN))
 
         tx_v3_child_3 = self.wallet.create_self_transfer_multi(
-            utxos_to_spend=[tx_v3_parent["new_utxos"][0], utxo_unrelated_conflict], fee_per_output=fee_to_beat_child2*5, version=3
+            utxos_to_spend=[tx_v3_parent["new_utxos"][0], utxo_unrelated_conflict], fee_per_output=fee_to_beat*2, version=3
         )
         node.sendrawtransaction(tx_v3_child_3["hex"])
         self.check_mempool(txids_v2_100 + [tx_v3_parent["txid"], tx_v3_child_3["txid"]])