[pycga] enable doc generation test for pyclaragenomics

[tijyojwad]

Python doc generation only happens successfully when the bindings have been built. However the current sphinx command doesn't fail when bindings aren't built. This issue is to investigate the right way to build sphinx based documentation and enable it in the tests so doc generation is validated on every PR.

[tijyojwad]

Consider using https://www.sphinx-doc.org/en/master/usage/advanced/setuptools.html instead of raw sphinx commands