docs: adjust punctuation characters for section headers

docs/source/index.rst

docs/source/inference/active_learning.rst

docs/source/inference/bayes_inference.rst

docs/source/inference/index.rst

docs/source/sampler/index.rst

docs/source/sampler/latin.rst

docs/source/sampler/metropolis_hastings.rst

docs/source/sampler/saltelli.rst

docs/source/sensitivity/index.rst

docs/source/sensitivity/sobol.rst

docs/source/simulator/index.rst

docs/source/simulator/mass_point_model.rst

docs/source/simulator/ravaflow24.rst

docs/source/simulator/run_simulator.rst