Fix links to arch-qualified package names

Fix links for lines such as:

Depends: bear/amd64 spdlog/amd64 (not considered)

The link spdlog/amd64 is as such:

https://release.debian.org/britney/update_excuses.html#spdlog

It's a broken link, it should be:

https://release.debian.org/britney/update_excuses.html#spdlog/amd64