Update stale and redirecting links

Validated all links with lychee and updated those that redirected
elsewhere to their canonical destinations:

- help.launchpad.net/Packaging/PPA -> documentation.ubuntu.com
  /launchpad/user/Packaging/PPA/
- github.com/Homebrew/homebrew-core/edit/master/Formula/libmaxminddb.rb
  -> .../blob/main/Formula/lib/libmaxminddb.rb (formula relocated under
  Formula/lib/ and default branch is now main; "Edit the file" step still
  applies from the blob page)
- ports.macports.org/port/libmaxminddb -> .../libmaxminddb/ (trailing
  slash)

Part of STF-557.

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

Author: oschwald

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://help.launchpad.net/Packaging/PPA for more details.
+https://documentation.ubuntu.com/launchpad/user/Packaging/PPA/ for more details.
 
 The PPA release script is at `dev-bin/ppa-release.sh`. Running it should guide
 you though the release, although it may require some changes to run on
@@ -40,7 +40,7 @@ non-trivial update to the formula or in the case where we want the Homebrew
 version updated promptly for some reason.
 
 - Go to
-  https://github.com/Homebrew/homebrew-core/edit/master/Formula/libmaxminddb.rb
+  https://github.com/Homebrew/homebrew-core/blob/main/Formula/lib/libmaxminddb.rb
 - Edit the file to update the url and sha256. You can get the sha256 for the
   tarball with the `sha256sum` command line utility.
 - Make a commit with the summary `libmaxminddb <VERSION>`

README.md

@@ -128,7 +128,7 @@ You can install libmaxminddb on macOS using [Homebrew](https://brew.sh):
 brew install libmaxminddb
 ```
 
-Or with [MacPorts](https://ports.macports.org/port/libmaxminddb):
+Or with [MacPorts](https://ports.macports.org/port/libmaxminddb/):
 
 ```bash
 sudo port install libmaxminddb