[MatL] Fracture/Coulomb. Drop anonymous namespace.

Not really need here and caused some warnings to appear
in the unity builds.

Warning were of type:
MaterialLib/FractureModels/Coulomb.cpp:182:38: warning: ‘MaterialLib::Fracture::Coulomb::Coulomb<DisplacementDim>::computeConstitutiveRelation(double, const ParameterLib::SpatialPosition&, double, Eigen::Ref<const Eigen::Matrix<double, -1, 1> >, Eigen::Ref<const Eigen::Matrix<double, -1, 1> >, Eigen::Ref<const Eigen::Matrix<double, -1, 1> >, Eigen::Ref<const Eigen::Matrix<double, -1, 1> >, Eigen::Ref<Eigen::Matrix<double, -1, 1> >, Eigen::Ref<Eigen::Matrix<double, -1, -1> >, typename MaterialLib::Fracture::FractureModelBase<DisplacementDim>::MaterialStateVariables&) [with int DisplacementDim = 3; typename MaterialLib::Fracture::FractureModelBase<DisplacementDim>::MaterialStateVariables = MaterialLib::Fracture::FractureModelBase<3>::MaterialStateVariables]::<lambda(const ResidualVectorType&)>’ has a field ‘MaterialLib::Fracture::Coulomb::Coulomb<DisplacementDim>::computeConstitutiveRelation(double, const ParameterLib::SpatialPosition&, double, Eigen::Ref<const Eigen::Matrix<double, -1, 1> >, Eigen::Ref<const Eigen::Matrix<double, -1, 1> >, Eigen::Ref<const Eigen::Matrix<double, -1, 1> >, Eigen::Ref<const Eigen::Matrix<double, -1, 1> >, Eigen::Ref<Eigen::Matrix<double, -1, 1> >, Eigen::Ref<Eigen::Matrix<double, -1, -1> >, typename MaterialLib::Fracture::FractureModelBase<DisplacementDim>::MaterialStateVariables&) [with int DisplacementDim = 3; typename MaterialLib::Fracture::FractureModelBase<DisplacementDim>::MaterialStateVariables = MaterialLib::Fracture::FractureModelBase<3>::MaterialStateVariables]::<lambda(const ResidualVectorType&)>::<mat capture>’ whose type uses the anonymous namespace [-Wsubobject-linkage]
  182 |         auto const update_solution = [&](ResidualVectorType const& increment) {