Remove links to empty docs from readme

[LilithHafner]

The docs are the README, so the README should not link to an external webpage that has no content.

Commented out instead of deleting in case folks add content to the Documenter.jl docs later.

I think I also automatically added a trailing newline because I used the GitHub web UI. Happy to revert that if needed.

[Azzaare]

Thanks!

We are in the process to centralize all the docs at https://juliaconstraints.github.io/

But it is not ready yet, so thank you again!

[LilithHafner]

It's plausible that this package's userbase may be centered on the the constraint based optimization ecosystem, in which case maybe it makes sense to have its docs not centralized with the rest of this org?

[Azzaare]

You're definitely correct. I was planning to have the doc available on both JuliaConstraints website and a standalone doc.

Ideally, it should be done before the PerfChecker.jl talk at the next JuliaCon