Fix hs61 test

[tmigot]

Close #72
Need JuliaSmoothOptimizers/NLPModelsJuMP.jl#181

[amontoison]

I already updated hs61 a few weeks ago.
f01b291

[tmigot]

Ok, but the issue remains because we also need to replace @NLconstraint by @constraint ...

[amontoison]

We need to do that only if we want to switch to the new API. It's related to the PR #321.

[tmigot]

Yes and no, using @constraint for quadratic constraint is possibly a better modeling, the fact that use @NLconstraint was a hack. I don't think this is particularly connected to the new API.
Thanks to the great work in NLPModelsJuMP we will be able to update quadratic constraints, that was the point of this. Also this PR was a draft, there was no need to merge it.

[amontoison]

@NLconstraint was mandatory for quadratic constraints before MOI, it was not a hack.
JuMP just added support for it later and us now.

The new API is now doing the same thing but for all nonlinear constraints /objective.

I merged the PR becasue we can test hs61 in all cases now, even with the old API.