Update paid group billing page

What does this MR do and why?

From discussion in #387305 (comment 1268261389), we're moving to standardize the free and non-free /billings pages by ensuring both utilize plans_data from CustomersDot. We do not intend to rely on CustomersDot as SSOT for copy.

Screenshots or screen recordings

before	after
	no change
	no change

How to set up and validate locally

• Sign up. Create new group.
• Go to Settings -> Billing page.
• Make sure correct features are listed under each plan.
• Start trial for this group. Go to Billing page again.
• Make sure correct features are listed under each plan.

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.

Related to #394395 (closed)