test: add rescan_utxos in MiniWallet's initialization

this simplifies usage when MiniWallet is used with a pre-mined chain.

test/functional/feature_fee_estimation.py

@@ -297,7 +297,6 @@ class EstimateFeeTest(BitcoinTestFramework):
         # Split two coinbases into many small utxos
         self.start_node(0)
         self.wallet = MiniWallet(self.nodes[0])
-        self.wallet.rescan_utxos()
         self.initial_split(self.nodes[0])
         self.log.info("Finished splitting")