QFutureInterface: remove comment that was never true

Even in the original patch where the comment was added the
callouts were made with the lock held.

Change-Id: Id8d122010d2195d83ddd4fdaf638f7fc4ac8163d
Reviewed-by: Ivan Solovev <ivan.solovev@qt.io>
Reviewed-by: Edward Welbourne <edward.welbourne@qt.io>

src/corelib/thread/qfutureinterface.cpp

@@ -800,8 +800,7 @@ void QFutureInterfaceBasePrivate::sendCallOuts(const QFutureCallOutEvent &callOu
 
 // This function connects an output interface (for example a QFutureWatcher)
 // to this future. While holding the lock we check the state and ready results
-// and add the appropriate callouts to the queue. In order to avoid deadlocks,
-// the actual callouts are made at the end while not holding the lock.
+// and add the appropriate callouts to the queue.
 void QFutureInterfaceBasePrivate::connectOutputInterface(QFutureCallOutInterface *iface)
 {
     QMutexLocker locker(&m_mutex);