Get rid of stale TODO comment

it was already chosen to follow the Method B (which accidentally
is the only proposed method in MQTT 5 Standard, by the way)

Change-Id: I55dcea0f9b10ef4e4e83e559369a40c802c34899
Reviewed-by: Maurice Kalinowski <maurice.kalinowski@qt.io>

src/mqtt/qmqttconnection.cpp

@@ -1636,8 +1636,6 @@ void QMqttConnection::finalize_pubrel()
 
     emit m_clientPrivate->m_client->messageStatusChanged(id, QMqtt::MessageStatus::Released, properties);
 
-    // ### TODO: send to our app now or not???
-    // See standard Figure 4.3 Method A or B ???
     sendControlPublishComp(id);
 }