
<!-- 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{"decodepsbt",
                "\nReturn a JSON object representing the serialized, base64-encoded partially signed Bitcoin transaction.\n",
                {
                    {"psbt", RPCArg::Type::STR, RPCArg::Optional::NO, "The PSBT base64 string"},
                },
                RPCResult{
                    RPCResult::Type::OBJ, "", "",
                    {
                        {RPCResult::Type::OBJ, "tx", "The decoded network-serialized unsigned transaction.",
                        {
                            {RPCResult::Type::ELISION, "", "The layout is the same as the output of decoderawtransaction."},
                        }},
                        {RPCResult::Type::OBJ_DYN, "unknown", "The unknown global fields",
                        {
                             {RPCResult::Type::STR_HEX, "key", "(key-value pair) An unknown key-value pair"},
                        }},
                        {RPCResult::Type::ARR, "inputs", "",
                        {
                            {RPCResult::Type::OBJ, "", "",
                            {
                                {RPCResult::Type::OBJ, "non_witness_utxo",  true, "Decoded network transaction for non-witness UTXOs",
                                {
                                    {RPCResult::Type::ELISION, "",""},
                                }},
                                {RPCResult::Type::OBJ, "witness_utxo",  true, "Transaction output for witness UTXOs",
                                {
                                    {RPCResult::Type::NUM, "amount", "The value in " + CURRENCY_UNIT},
                                    {RPCResult::Type::OBJ, "scriptPubKey", "",