[macOS] remove Growl support, remove unused code

src/qt/macnotificationhandler.h

@@ -7,20 +7,17 @@
 
 #include <QObject>
 
-/** Macintosh-specific notification handler (supports UserNotificationCenter and Growl).
+/** Macintosh-specific notification handler (supports UserNotificationCenter).
  */
 class MacNotificationHandler : public QObject
 {
     Q_OBJECT
 
 public:
-    /** shows a 10.8+ UserNotification in the UserNotificationCenter
+    /** shows a macOS 10.8+ UserNotification in the UserNotificationCenter
      */
     void showNotification(const QString &title, const QString &text);
 
-    /** executes AppleScript */
-    void sendAppleScript(const QString &script);
-
     /** check if OS can handle UserNotifications */
     bool hasUserNotificationCenterSupport(void);
     static MacNotificationHandler *instance();