Fix the subject of notifications

lib/private/notification/manager.php

@@ -141,7 +141,7 @@ class Manager implements IManager {
 
 		foreach ($notifiers as $notifier) {
 			try {
-				$notifier->prepare($notification, $languageCode);
+				$notification = $notifier->prepare($notification, $languageCode);
 			} catch (\InvalidArgumentException $e) {
 				continue;
 			}

lib/private/notification/notification.php

@@ -248,7 +248,7 @@ class Notification implements INotification {
 	 * @since 8.2.0
 	 */
 	public function getParsedSubject() {
-		return $this->messageParsed;
+		return $this->subjectParsed;
 	}
 
 	/**