qt, refactor: simplify third-party tx url action through overload

Simplify the creation, addition, and slot/signal connection of
a third part tx url context menu action by using an overloaded
addAction function.

src/qt/transactionview.cpp

@@ -228,11 +228,9 @@ void TransactionView::setModel(WalletModel *_model)
                 QString host = QUrl(url, QUrl::StrictMode).host();
                 if (!host.isEmpty())
                 {
-                    QAction *thirdPartyTxUrlAction = new QAction(host, this); // use host as menu item label
                     if (i == 0)
                         contextMenu->addSeparator();
-                    contextMenu->addAction(thirdPartyTxUrlAction);
-                    connect(thirdPartyTxUrlAction, &QAction::triggered, [this, url] { openThirdPartyTxUrl(url); });
+                    contextMenu->addAction(host, [this, url] { openThirdPartyTxUrl(url); });
                 }
             }
         }