Update public list archives link in 9.16.3

[MMeent]

Currently, it links to https://cabforum.org/pipermail/public/, whereas the actual location is at https://archive.cabforum.org/pipermail/public/. There is a redirect in place, but I believe direct linking would be preferred.

[sleevi]

Note: I moved this to the Forum level repository, rather than servercert, as although this is specifically about updating in the BRs (very much a servercert issue), the broader issue of updating links (e.g. including the website) is arguably an Infrastructure WG issue to sort through and flag for how WGs can consider.