Fixes bitcoin#26490 by preventing notifications

MacOS 13 sends a window focus change notification after the main
window has been destroyed but before the QTApplication has been
destroyed. This results in the menu bar receiving a notification
despite it no longer existing. The solution is to pass the main
window as context when subscribing to the notifications. Qt
automatically unsubscribes to notifications if the sender OR
context is destroyed.

Github-Pull: bitcoin-core/gui#680
Rebased-From: 8a5014c
(cherry picked from commit 272fa25)

Author: john-moffett

src/qt/bitcoingui.cpp

@@ -483,7 +483,7 @@ void BitcoinGUI::createMenuBar()
     connect(minimize_action, &QAction::triggered, [] {
         QApplication::activeWindow()->showMinimized();
     });
-    connect(qApp, &QApplication::focusWindowChanged, [minimize_action] (QWindow* window) {
+    connect(qApp, &QApplication::focusWindowChanged, this, [minimize_action] (QWindow* window) {
         minimize_action->setEnabled(window != nullptr && (window->flags() & Qt::Dialog) != Qt::Dialog && window->windowState() != Qt::WindowMinimized);
     });
 
@@ -498,7 +498,7 @@ void BitcoinGUI::createMenuBar()
         }
     });
 
-    connect(qApp, &QApplication::focusWindowChanged, [zoom_action] (QWindow* window) {
+    connect(qApp, &QApplication::focusWindowChanged, this, [zoom_action] (QWindow* window) {
         zoom_action->setEnabled(window != nullptr);
     });
 #endif