Fig18.7 (Book2) add `gprDemoNoiseFreeAndNoisy.ipynb` (#728)
Fig18.7 (Book2) add `gprDemoNoiseFreeAndNoisy.ipynb` (#728)

* add `gprDemoNoiseFreeAndNoisy.ipynb`

* despine
probml/pyprobml,probml/pyprobml,probml/pyprobml,probml/pyprobml