bpo-32800: Update link to w3c doc for xml default namespaces (GH-5609) (GH-5611)

The new link is given in a red box on the old page.
(cherry picked from commit 8d1f2f40389c476d9240ec87a33da0373597c6af)

Co-authored-by: sblondon <sblondon@users.noreply.github.com>
2 files changed