qt: Leverage the default "Create new receiving address" button

When Enter or Return is pressed the default button will be always
clicked. All buttons can always be clicked from the keyboard by pressing
spacebar when the button has focus.

src/qt/receivecoinsdialog.cpp

@@ -242,22 +242,6 @@ void ReceiveCoinsDialog::resizeEvent(QResizeEvent *event)
     columnResizingFixer->stretchColumnWidth(RecentRequestsTableModel::Message);
 }
 
-void ReceiveCoinsDialog::keyPressEvent(QKeyEvent *event)
-{
-    if (event->key() == Qt::Key_Return)
-    {
-        // press return -> submit form
-        if (ui->reqLabel->hasFocus() || ui->reqAmount->hasFocus() || ui->reqMessage->hasFocus())
-        {
-            event->ignore();
-            on_receiveButton_clicked();
-            return;
-        }
-    }
-
-    this->QDialog::keyPressEvent(event);
-}
-
 QModelIndex ReceiveCoinsDialog::selectedRow()
 {
     if(!model || !model->getRecentRequestsTableModel() || !ui->recentRequestsView->selectionModel())

src/qt/receivecoinsdialog.h

@@ -49,9 +49,6 @@ public Q_SLOTS:
     void reject() override;
     void accept() override;
 
-protected:
-    virtual void keyPressEvent(QKeyEvent *event) override;
-
 private:
     Ui::ReceiveCoinsDialog *ui;
     GUIUtil::TableViewLastColumnResizingFixer *columnResizingFixer;