Doc: update the note about nested deleteLater()

If you enter a nested event loop, cause a deleteLater(), exit that event
loop, then enter a new one, the nesting count will be the same so those
are legitimate targets for deletion.

Task-number: QTBUG-73432
Change-Id: Id98140e1c2f0426cabbefffd157f975b5e291ccd
Reviewed-by: Paul Wicking <paul.wicking@qt.io>
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

src/corelib/kernel/qobject.cpp

@@ -2171,8 +2171,10 @@ void QObject::removeEventFilter(QObject *obj)
 
     Note that entering and leaving a new event loop (e.g., by opening a modal
     dialog) will \e not perform the deferred deletion; for the object to be
-    deleted, the control must return to the event loop from which
-    deleteLater() was called.
+    deleted, the control must return to the event loop from which deleteLater()
+    was called. This does not apply to objects deleted while a previous, nested
+    event loop was still running: the Qt event loop will delete those objects
+    as soon as the new nested event loop starts.
 
     \b{Note:} It is safe to call this function more than once; when the
     first deferred deletion event is delivered, any pending events for the