Use 'scikit-learn' rather than 'sklearn' in ci-runner

[edknv]

ci-runner build currently failing due to:

    The 'sklearn' PyPI package is deprecated, use 'scikit-learn'
    rather than 'sklearn' for pip commands.
    
    Here is how to fix this error in the main use cases:
    - use 'pip install scikit-learn' rather than 'pip install sklearn'
    - replace 'sklearn' by 'scikit-learn' in your pip requirements files
      (requirements.txt, setup.py, setup.cfg, Pipfile, etc ...)
    - if the 'sklearn' package is used by one of your dependencies,
      it would be great if you take some time to track which package uses
      'sklearn' instead of 'scikit-learn' and report it to their issue tracker
    - as a last resort, set the environment variable
      SKLEARN_ALLOW_DEPRECATED_SKLEARN_PACKAGE_INSTALL=True to avoid this error

[github-actions]

Documentation preview

https://nvidia-merlin.github.io/Merlin/review/pr-860