More cleanup

src/bayesvalidrox/surrogate_models/reg_fast_ard.py

src/bayesvalidrox/surrogate_models/sequential_design.py

src/bayesvalidrox/surrogate_models/surrogate_models.py

tests/test_BayesInference.py

tests/test_Engine.py

tests/test_ExpDesign.py

tests/test_Input.py

tests/test_InputSpace.py

tests/test_MCMC.py

tests/test_MetaModel.py