Unbreak Documenter for the Julia manual and make sure it stays that way #2806
Description
The Julia documentation is currently still being built with Documenter 1.11.4 which is a pity as of course we'd like it to benefit from improvements being made here (esp. those going into the next release).
As far as I can tell this is due to the problem described here, i.e., Documenter hangs.
An attempted fix is in #2710 but that's still not merged. We either need to get that one complete, or implement the alternative fix discussed on that PR.
Beyond that, it would certainly be a good idea if we built the Julia manual as part of our CI tests; if not on every PR then at least as part of the regression tests. Work on this was begun in #2724 but needs to be completed.