Remove obj_c for macOS Dock icon menu

Qt `setAsDockMenu()` does this work.

src/qt/bitcoingui.cpp

@@ -607,7 +607,9 @@ void BitcoinGUI::createTrayIconMenu()
     // Note: On macOS, the Dock icon is used to provide the tray's functionality.
     MacDockIconHandler *dockIconHandler = MacDockIconHandler::instance();
     connect(dockIconHandler, &MacDockIconHandler::dockIconClicked, this, &BitcoinGUI::macosDockIconActivated);
-    trayIconMenu = dockIconHandler->dockMenu();
+
+    trayIconMenu = new QMenu(this);
+    trayIconMenu->setAsDockMenu();
 #endif
 
     // Configuration of the tray icon (or Dock icon) menu

src/qt/macdockiconhandler.h

@@ -7,11 +7,6 @@
 
 #include <QObject>
 
-QT_BEGIN_NAMESPACE
-class QMenu;
-class QWidget;
-QT_END_NAMESPACE
-
 /** macOS-specific Dock icon handler.
  */
 class MacDockIconHandler : public QObject
@@ -19,9 +14,6 @@ class MacDockIconHandler : public QObject
     Q_OBJECT
 
 public:
-    ~MacDockIconHandler();
-
-    QMenu *dockMenu();
     static MacDockIconHandler *instance();
     static void cleanup();
 
@@ -30,9 +22,6 @@ Q_SIGNALS:
 
 private:
     MacDockIconHandler();
-
-    QWidget *m_dummyWidget;
-    QMenu *m_dockMenu;
 };
 
 #endif // BITCOIN_QT_MACDOCKICONHANDLER_H

src/qt/macdockiconhandler.mm

@@ -4,17 +4,13 @@
 
 #include "macdockiconhandler.h"
 
-#include <QMenu>
-#include <QWidget>
-
 #undef slots
-#include <Cocoa/Cocoa.h>
 #include <objc/objc.h>
 #include <objc/message.h>
 
 static MacDockIconHandler *s_instance = nullptr;
 
-bool dockClickHandler(id self,SEL _cmd,...) {
+bool dockClickHandler(id self, SEL _cmd, ...) {
     Q_UNUSED(self)
     Q_UNUSED(_cmd)
 
@@ -32,28 +28,9 @@ void setupDockClickHandler() {
     class_replaceMethod(delClass, shouldHandle, (IMP)dockClickHandler, "B@:");
 }
 
-
 MacDockIconHandler::MacDockIconHandler() : QObject()
 {
-    NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init];
-
     setupDockClickHandler();
-    this->m_dummyWidget = new QWidget();
-    this->m_dockMenu = new QMenu(this->m_dummyWidget);
-#if QT_VERSION >= 0x050200
-    this->m_dockMenu->setAsDockMenu();
-#endif
-    [pool release];
-}
-
-MacDockIconHandler::~MacDockIconHandler()
-{
-    delete this->m_dummyWidget;
-}
-
-QMenu *MacDockIconHandler::dockMenu()
-{
-    return this->m_dockMenu;
 }
 
 MacDockIconHandler *MacDockIconHandler::instance()