Doc: Mark QQuickWebEngineScript::timerEvent() internal

...to suppress a QDoc error.

Change-Id: I11cb449137af06e11ba4e14a14da97d0088f8416
Reviewed-by: Michael Brüning <michael.bruning@qt.io>

src/webengine/api/qquickwebenginescript.cpp

@@ -403,6 +403,9 @@ void QQuickWebEngineScript::setRunOnSubframes(bool on)
     Q_EMIT runOnSubframesChanged(on);
 }
 
+/*!
+    \internal
+*/
 void QQuickWebEngineScript::timerEvent(QTimerEvent *e)
 {
     Q_D(QQuickWebEngineScript);