fix(styles): update hover token value for date picker

[abbeyhrt]

REF #10414

Updates token from background-hover to layer-hover because the hover state in g90 and g100 in v11 was too dark. Applies to the hover state for the next/previous month buttons, the day buttons, and the current month.

See #10414 (comment) for more context

Testing / Reviewing

Verify that the hover states in g90 and g100 for DatePicker match that of v10 DatePicker

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