wallet: remove unused SignatureData instances in spkm's FillPSBT methods

These are filled with signature data from a PSBT input, but not used anywhere
after, hence they can be removed.

Author: theStack

src/wallet/scriptpubkeyman.cpp

@@ -652,8 +652,6 @@ TransactionError LegacyScriptPubKeyMan::FillPSBT(PartiallySignedTransaction& psb
             // There's no UTXO so we can just skip this now
             continue;
         }
-        SignatureData sigdata;
-        input.FillSignatureData(sigdata);
         SignPSBTInput(HidingSigningProvider(this, !sign, !bip32derivs), psbtx, i, &txdata, sighash_type, nullptr, finalize);
 
         bool signed_one = PSBTInputSigned(input);
@@ -2520,8 +2518,6 @@ TransactionError DescriptorScriptPubKeyMan::FillPSBT(PartiallySignedTransaction&
             // There's no UTXO so we can just skip this now
             continue;
         }
-        SignatureData sigdata;
-        input.FillSignatureData(sigdata);
 
         std::unique_ptr<FlatSigningProvider> keys = std::make_unique<FlatSigningProvider>();
         std::unique_ptr<FlatSigningProvider> script_keys = GetSigningProvider(script, /*include_private=*/sign);