test: Make the scriptPubKey of MiniWallet created txs mutable

This makes individual bytes of the scriptPubKey mutable, previously it
could only be re-assigned as a whole.

Author: MacroFake

test/functional/test_framework/wallet.py

@@ -294,7 +294,7 @@ def create_self_transfer(self, *, fee_rate=Decimal("0.003"), fee=Decimal("0"), u
 
         tx = CTransaction()
         tx.vin = [CTxIn(COutPoint(int(utxo_to_spend['txid'], 16), utxo_to_spend['vout']), nSequence=sequence)]
-        tx.vout = [CTxOut(int(COIN * send_value), self._scriptPubKey)]
+        tx.vout = [CTxOut(int(COIN * send_value), bytearray(self._scriptPubKey))]
         tx.nLockTime = locktime
         if self._mode == MiniWalletMode.RAW_P2PK:
             self.sign_tx(tx)