docs: fix dead URL in urllib.robotparser documentation

Author: yosofbadr

Doc/library/urllib.robotparser.rst

@@ -18,7 +18,7 @@
 This module provides a single class, :class:`RobotFileParser`, which answers
 questions about whether or not a particular user agent can fetch a URL on the
 website that published the :file:`robots.txt` file.  For more details on the
-structure of :file:`robots.txt` files, see http://www.robotstxt.org/orig.html.
+structure of :file:`robots.txt` files, see https://datatracker.ietf.org/doc/html/rfc9309.
 
 
 .. class:: RobotFileParser(url='')