Update billing management text

[GiselleNessi]

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PR-Codex overview

This PR focuses on updating the PlanInfoCard component in the billing settings of the dashboard. It enhances the layout and adds informative text to improve user experience.

Detailed summary

• Changed the inner div from flex items-center to flex flex-col items-start.
• Added a new paragraph with instructions for managing billing.
• Updated the variant prop of the BillingPortalButton from outline to primary.

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