Warning with MOIObjectiveBackend

```julia
  1 dependency had output during precompilation:
┌ PartiallySeparableNLPModels
│  WARNING: method definition for #MOIObjectiveBackend#2 at /home/alexis/Bureau/git/PartiallySeparableNLPModels.jl/src/backends/ObjectiveBackends/MOIObjectiveBackend.jl:19 declares type variable T but does not use it.
└  
```