gh-141444: Replace dead URL in urllib.robotparser example

Replace the defunct musi-cal.com URL with python.org in the
RobotFileParser documentation example. The old URL is no longer
active and the example output was specific to that site's
robots.txt file.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Author: kovan

Doc/library/urllib.robotparser.rst

@@ -91,16 +91,7 @@ class::
 
    >>> import urllib.robotparser
    >>> rp = urllib.robotparser.RobotFileParser()
-   >>> rp.set_url("http://www.musi-cal.com/robots.txt")
+   >>> rp.set_url("http://www.python.org/robots.txt")
    >>> rp.read()
-   >>> rrate = rp.request_rate("*")
-   >>> rrate.requests
-   3
-   >>> rrate.seconds
-   20
-   >>> rp.crawl_delay("*")
-   6
-   >>> rp.can_fetch("*", "http://www.musi-cal.com/cgi-bin/search?city=San+Francisco")
-   False
-   >>> rp.can_fetch("*", "http://www.musi-cal.com/")
+   >>> rp.can_fetch("*", "http://www.python.org/")
    True