doc fix for unattended debian/ubuntu installer linkrot

the links for chef-maintained preseeds/autoinstallers for debian/ubuntu both rotted. i'm just getting started with packer, so i hope this edit is accurate.

website/content/guides/automatic-operating-system-installs/preseed_ubuntu.mdx

@@ -171,6 +171,4 @@ containing the "http" directory.
   ],
 ```
 
-For more functional examples of a debian preseeded installation, you can see the
-Chef-maintained bento boxes for [Debian](https://github.com/chef/bento/tree/master/packer_templates/debian)
-and [Ubuntu](https://github.com/chef/bento/tree/master/packer_templates/ubuntu)
+For more functional examples of a Debian preseeded installation, you can see the Chef-maintained [bento](https://github.com/chef/bento?tab=readme-ov-file#using-packer) box [preseed](https://github.com/chef/bento/blob/6fe9fa20d1f37e916a7babdee87c89ba38ce54a4/packer_templates/http/debian/preseed.cfg), the Ubuntu [autoinstall config](https://github.com/chef/bento/blob/6fe9fa20d1f37e916a7babdee87c89ba38ce54a4/packer_templates/http/ubuntu/user-data), their [builders](https://github.com/chef/bento/blob/6fe9fa20d1f37e916a7babdee87c89ba38ce54a4/packer_templates/pkr-builder.pkr.hcl), or the legacy .json templates for [Debian](https://web.archive.org/web/20220508073539mp_/https://github.com/chef/bento/blob/main/packer_templates/debian/debian-10.11-amd64.json) and [Ubuntu](https://web.archive.org/web/20211101220217/https://github.com/chef/bento/blob/main/packer_templates/ubuntu/ubuntu-20.04-amd64.json).