Notification: Use system email address as notification sender

Problem: Many Yobi users had extracted and filtered notification
messages of Yobi from their mailbox by using MUA which supports
groupping by the sender's email address. But if
application.notification.bymail.hideaddress is false, it did not work
because the sender's email address is the user's who causes the
notification.

Solution: Use system email address as the sender's email address of
notification messages even if
application.notification.bymail.hideaddress is false.

app/models/NotificationMail.java

@@ -240,12 +240,8 @@ private static void sendNotification(NotificationEvent event) {
             final EventEmail email = new EventEmail(event);
 
             try {
-                if (hideAddress) {
-                    email.setFrom(Config.getEmailFromSmtp(), event.getSender().name);
-                    email.addTo(Config.getEmailFromSmtp(), utils.Config.getSiteName());
-                } else {
-                    email.setFrom(event.getSender().email, event.getSender().name);
-                }
+                email.setFrom(Config.getEmailFromSmtp(), event.getSender().name);
+                email.addTo(Config.getEmailFromSmtp(), utils.Config.getSiteName());
 
                 for (User receiver : usersByLang.get(langCode)) {
                     if (hideAddress) {