Upgrade antora to supported version

[Jane Sandberg]

We're currently on antora 2. However, antora considers antora 2 to be EOL, and only maintains documentation for antora 3.0 and antora 3.1 at this time. We should upgrade, so we can refer to the documentation when working with antora.

It looks like the lunr integration is improved, so we can use the lunr plugin, rather than using --generator antora-site-generator-lunr

Here are some docs for how to upgrade: https://docs.antora.org/antora/latest/install/upgrade-antora/

[Jane Sandberg (sandbergja)]

Here is a collab branch that we started in today's DIG meeting: https://git.evergreen-ils.org/?p=working/Evergreen.git;a=shortlog;h=refs/heads/collab/sandbergja/lp2036328-antora-3.1

It's ready for testing; looking forward to hearing how testing goes!

[Galen Charlton (gmc)]

Signoff pushed to user/gmcharlt/lp2036328_signoff. It includes a follow-up that does some cleaning before installing Antora, as the 2.3 CLI from a previous build was getting used instead (and failing).

I consider that cleanup a stopgap; if we can come up with a better way so that we don't have to reinstall so much from scratch each time generate_docs.pl is used, that will save time for people who need to repeatedly build the docs.

[Jane Sandberg (sandbergja)]

Thanks, Galen and DIG. I've pushed this to rel_3_11 and above. I know this was considered a Wishlist bug, but backporting it will cause fewer errors when it attempts to generate docs for 3.12 and 3.11.