Update info on the colors param

[ethanpalm]

Documentation changes

The info on https://mintlify.com/docs/settings#param-colors is inaccurate right now. This PR corrects the section to explain that light and dark are setting the light and dark colors for the theme and do not have an influence on light or dark mode.

Closes https://linear.app/mintlify/issue/DOC-72/update-colors-section-of-settings

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