gh-103417: use time.monotonic in the example for sched.scheduler (#103418)

Author: nburns

Doc/library/sched.rst

@@ -36,7 +36,7 @@ scheduler:
 Example::
 
    >>> import sched, time
-   >>> s = sched.scheduler(time.time, time.sleep)
+   >>> s = sched.scheduler(time.monotonic, time.sleep)
    >>> def print_time(a='default'):
    ...     print("From print_time", time.time(), a)
    ...