
<!-- Describe the issue -->
Following commit 46004790588c24174a0bec49b540d158ce163ffd (@achow101), `decodepsbt` overstates the fee, apparently including both the `witness_utxo` and `non_witness_utxo` amounts in the inputs.

**Expected behavior**

The decoded fee should be the sum of the inputs, minus the sum of the outputs.

**Actual behavior**

The decoded fee is exactly twice the amount of the inputs, minus the sum of the outputs.

**To reproduce**

Build any PSBT using `createpsbt`, `walletprocesspsbt`, then decode it with `decodepsbt`. See the `fee` field in the JSON.

**System information**

I compiled myself from 5550fa5983ea59e7ccef6540b7ec49a1770fb3ca on Whonix 14.

Then I did `git revert 46004790588c24174a0bec49b540d158ce163ffd ` and the problem went away.

{
    RPCHelpMan{"testmempoolaccept",
                "\nReturns result of mempool acceptance tests indicating if raw transaction (serialized, hex-encoded) would be accepted by mempool.\n"
                "\nThis checks if the transaction violates the consensus or policy rules.\n"
                "\nSee sendrawtransaction call.\n",
                {
                    {"rawtxs", RPCArg::Type::ARR, RPCArg::Optional::NO, "An array of hex strings of raw transactions.\n"
            "                                        Length must be one for now.",
                        {
                            {"rawtx", RPCArg::Type::STR_HEX, RPCArg::Optional::OMITTED, ""},
                        },
                        },
                    {"maxfeerate", RPCArg::Type::AMOUNT,  FormatMoney(DEFAULT_MAX_RAW_TX_FEE_RATE.GetFeePerK()), "Reject transactions whose fee rate is higher than the specified value, expressed in " + CURRENCY_UNIT + "/kB\n"},
                },
                RPCResult{
                    RPCResult::Type::ARR, "", "The result of the mempool acceptance test for each raw transaction in the input array.\n"
                        "Length is exactly one for now.",
                    {
                        {RPCResult::Type::OBJ, "", "",
                        {
                            {RPCResult::Type::STR_HEX, "txid", "The transaction hash in hex"},
                            {RPCResult::Type::BOOL, "allowed", "If the mempool allows this tx to be inserted"},