Remove `sklearn=0.0` package from scikit-learn easybuilds

[tovrstra]

The presence of this package makes it difficult to reproduce with pip a software environment loaded with lmod. I would suggest to remove it from the eb files.

As of 2022, the installation of the dummy sklearn package is no longer supported. (Before, it was essentially a wrapper for the proper scikit-learn package.) If you try to install sklearn now in with pip, you get:

pip install --dry-run sklearn
Defaulting to user installation because normal site-packages is not writeable
Collecting sklearn
  Downloading sklearn-0.0.post12.tar.gz (2.6 kB)
  Installing build dependencies ... done
  Getting requirements to build wheel ... error
  error: subprocess-exited-with-error
  
  × Getting requirements to build wheel did not run successfully.
  │ exit code: 1
  ╰─> [15 lines of output]
      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
      
      More information is available at
      https://github.com/scikit-learn/sklearn-pypi-package
      [end of output]
  
  note: This error originates from a subprocess, and is likely not a problem with pip.

(@boegel This is also part of a preparation for a software install request.)

[boegel]

I think it makes sense to try and avoid using sklearn, and see what trouble that causes for stuff that depends on scikit-learn.
If they still use sklearn in their requirements.txt (or whatever), we can patch that easily to scikit-learn.