upgrade @adobe/react-spectrum which now comes with the slider component

[mburri]

The slider component was pushed out of alpha and is now part of @adobe/react-spectrum with the new 3.7.0 release.

• [x] upgrade to @adobe/react-spectrum 3.7.0
• [x] remove dependency to react-spectrum/slider (alpha)
• [x] import the slider component from @adobe/react-spectrum