Fix failing CI on building docs

[jamesrswift]

CI automatically builds the docs, which depend on a locally installed unreleased version of mantis. This issue could be resolved by either not requiring that CI successfully compiles the docs, or by some means installing this package during CI.

[tingerrr]

It's also a little problematic for contributors who wish to view their changes to the docs.

I would like to use utpm for management of pre-release versions of Typst packages, but I don't know if it's mature enough yet. The last commit was 3 months ago and when I tried it, it had some weird bugs.

Perhaps I could flesh utpm out to add the necessary features and fix the bugs I encountered with it. I don't think git packages are expected to hit anytime soon in Typst itself, so this may be necessary in the long run anyway.

[jamesrswift]

In meantime then, I'll disable it from the CI as it is getting in the way a bit at the moment

[tingerrr]

Sounds good, just remove the docs dependency on the ci recipe for now.