make the model comparison example run.

examples/model-comparison/L2_model.py

examples/model-comparison/NL4_model.py

examples/model-comparison/test_model_comparison.py

src/bayesvalidrox/bayes_inference/bayes_inference.py

src/bayesvalidrox/bayes_inference/bayes_model_comparison.py

src/bayesvalidrox/pylink/pylink.py

src/bayesvalidrox/surrogate_models/exp_designs.py

src/bayesvalidrox/surrogate_models/surrogate_models.py