Update PPA docs link to its canonical destination

The Launchpad PPA documentation URL now 301-redirects from
documentation.ubuntu.com to ubuntu.com/docs, which the link checker
rejects since max_redirects is 0. Point at the canonical destination.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: horgh

README.dev.md

@@ -20,7 +20,7 @@ You may want to refer to the section about prerequisites.
 In order to upload a PPA, you have to create a launchpad.net account and
 register a GPG key with that account. You also need to be added to the MaxMind
 team. Ask in the dev channel for someone to add you. See
-https://documentation.ubuntu.com/launchpad/user/reference/packaging/ppas/ppa/
+https://ubuntu.com/docs/launchpad/user/reference/packaging/ppas/ppa/
 for more details.
 
 The PPA release script is at `dev-bin/ppa-release.sh`. Running it should guide