Merge bitcoin/bitcoin#32138: wallet, rpc: remove settxfee and paytxfee

24f93c9af7 release note (Pol Espinasa)
331a5279d2 wallet, rpc:remove settxfee and paytxfee (Pol Espinasa)

Pull request description:

  **Summary**

  This PR removes the settxfee RPC and paytxfee setting (Bitcoin Core 31.0).
  These two features were deprecated in https://github.com/bitcoin/bitcoin/pull/31278.

ACKs for top commit:
  achow101:
    ACK 24f93c9af7
  w0xlt:
    reACK 24f93c9af7

Tree-SHA512: e090f1a72ba2cbeba7c982dd51dfdcf6baf0a164827337cf56fd85f733e143b8d6116b8cd53c59c812cacef193dfa0b101a830fc455e32bf225e8505e7b2a554

src/qt/sendcoinsdialog.cpp

@@ -40,7 +40,6 @@
 
 using common::PSBTError;
 using wallet::CCoinControl;
-using wallet::DEFAULT_PAY_TX_FEE;
 
 static constexpr std::array confTargets{2, 4, 6, 12, 24, 48, 144, 504, 1008};
 int getConfTargetForIndex(int index) {
@@ -125,8 +124,6 @@ SendCoinsDialog::SendCoinsDialog(const PlatformStyle *_platformStyle, QWidget *p
         settings.setValue("nFeeRadio", 0); // recommended
     if (!settings.contains("nSmartFeeSliderPosition"))
         settings.setValue("nSmartFeeSliderPosition", 0);
-    if (!settings.contains("nTransactionFee"))
-        settings.setValue("nTransactionFee", (qint64)DEFAULT_PAY_TX_FEE);
     ui->groupFee->setId(ui->radioSmartFee, 0);
     ui->groupFee->setId(ui->radioCustomFee, 1);
     ui->groupFee->button((int)std::max(0, std::min(1, settings.value("nFeeRadio").toInt())))->setChecked(true);