librascal still refers to deprecated skcosmo instead of skmatter

[cbenmahm]

When importing FPS or CUR using from rascal.utils import CURFilter, FPSFilter, we get the warning : Warning: skcosmo module not found. CUR and FPS filters will be unavailable..

Then, by installing skcosmo using pip install skcosmo and trying to import the filters again, we get another warning :

DeprecationWarning: This package has been renamed to scikit-matter (skmatter https://github.com/lab-cosmo/scikit-matter). This package will no longer be maintained and updated. Please install the new package using `pip install skmatter`