[3.14] gh-141412: Use reliable target URL for urllib example (GH-141428)

[miss-islington]

The endpoint used for demonstrating reading URLs is no longer
stable. This change substitutes a target over which we have more
control.
(cherry picked from commit fbcac79)

Co-authored-by: Bob Kline bkline@users.noreply.github.com

• Issue: URL for tutorial urlopen example ~is dead~ doesn't want to go on the cart #141412

---

📚 Documentation preview 📚: https://cpython-previews--141474.org.readthedocs.build/

[python-cla-bot]

All commit authors signed the Contributor License Agreement.

[zware]

The following commit authors need to sign the Contributor License Agreement:

* [bkline@users.noreply.github.com](mailto:bkline@users.noreply.github.com)

@bkline could I trouble you to click through the CLA process again to add the referenced noreply address? This is due to the way GitHub rewrites things when creating a squash merge.