Only store input data in a single place in the repo

[fedarko]

There are duplicated versions of the "sleep apnea" and "red sea" test datasets in this repository right now. They're contained in both qurro/tests/input/ and example_notebooks/.../input/ (sleep apnea is used for the DEICODE notebook, and red sea is used for the songbird notebook).

We should probably only store these datasets in the example_notebooks locations. I remember in the past they were only stored in the qurro/tests/input folder, which resulted in some long filenames in the notebooks.

...either way, though, just eliminating this redundancy would be good.