Fix issues with notebooks

[aamster]

This PR fixes issues with the notebooks so that all run successfully and the notebook runner workflow job passes.

• Fixes an issue with ProjectCacheBase

Error case:

    cache.load_manifest(
        'visual-behavior-neuropixels_project_manifest_v0.2.0.json')
    cache.load_latest_manifest()

The last line was not loading the latest metadata tables into memory, since the previous line was loading the old ones.
The fix is to call load_manifest in load_latest_manifest

• sklearn is called "scikit-learn" on pypi, not "sklearn"
• bug in visual_behavior_mouse_history notebook: don't modify a property

[review-notebook-app]

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[morriscb]

Looks good to me.