Fix displaying the actual plan name on the billings page

What does this MR do?

We merge extend/reactivate button data and this hash contains the plan_name key which overwrites the actual plan name with the Ultimate plan name.

Closes https://gitlab.com/gitlab-org/customers-gitlab-com/-/issues/3434

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N/A

How to setup and validate locally (strongly suggested)

Does this MR meet the acceptance criteria?

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