change `ValueError` to `RuntimeWarning` when `n_dim < n_informative`

[sampan501]

Closes #278

Changes proposed in this pull request:

• Sets n_informative to n_dim when n_dim < n_informative
• Raises a RuntimeWarning

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[sampan501]

I think errors are related to some issue with spin and not this PR

[sampan501]

3.11 seems too new.

I only did it since I thought it might be able to fix doc build issues, but it did not