bpo-36270: Doc: add link to traceback object reference (GH-13119)

Doc/library/sys.rst

@@ -345,7 +345,7 @@ always available.
    ``(type, value, traceback)``.  Their meaning is: *type* gets the type of the
    exception being handled (a subclass of :exc:`BaseException`); *value* gets
    the exception instance (an instance of the exception type); *traceback* gets
-   a traceback object (see the Reference Manual) which encapsulates the call
+   a :ref:`traceback object <traceback-objects>` which encapsulates the call
    stack at the point where the exception originally occurred.