Docs are not building currently because something in the mulit-objective optimisation section of examples/optim.jl is failing.

The run starts the optimisation but never gets to the point of outputting the first set of data. This has happened to me before with BBO, but I'm not sure of the fix. Odd thing is that it's only recently happened in our example file. It's not a Julia 1.5 v 1.6 issue, it's not a recent BBO version issue (master and the current release have the problem), its not a github runner changed OS versions recently (since it's also failing on my local machine).

I need to do a hunt of recent changes to our internals to see if its our fault. In #467 I'm thinking I could just bake in the result and not run the example for now until the issue is resolved. That'll mean both Optim and Zombies will be on the list of examples we need to take care of manually until this is resolved.