gui: correct replacement of amp character in the wallet name for QMenu

The comment in the code regarding the use of an "&"
on a menu item is misleading. If a wallet name has an "&" in it,
it is not supposed to be interpreted as a hot-key, but it should be
shown as it is without replacing it to an underscore.

src/qt/bitcoingui.cpp

@@ -399,10 +399,9 @@ void BitcoinGUI::createActions()
             for (const std::pair<const std::string, bool>& i : m_wallet_controller->listWalletDir()) {
                 const std::string& path = i.first;
                 QString name = path.empty() ? QString("["+tr("default wallet")+"]") : QString::fromStdString(path);
-                // Menu items remove single &. Single & are shown when && is in
-                // the string, but only the first occurrence. So replace only
-                // the first & with &&.
-                name.replace(name.indexOf(QChar('&')), 1, QString("&&"));
+                // An single ampersand in the menu item's text sets a shortcut for this item.
+                // Single & are shown when && is in the string. So replace & with &&.
+                name.replace(QChar('&'), QString("&&"));
                 QAction* action = m_open_wallet_menu->addAction(name);
 
                 if (i.second) {