Conditionally display user data on GitLab Credits Dashboard

What does this MR do and why?

This MR hides user data in the GitLab Credits dashboard depending on the value of display_gitlab_credits_user_data.

This is to support https://gitlab.com/gitlab-org/gitlab/-/issues/580868+

MR Cadence

Description	MR
Add display_gitlab_credits_user_data to app and namespace settings	!214508 (merged)
Make display_gitlab_credits_user_data configurable in admin area	!214538 (merged)
Allow groups to update display_gitlab_credits_user_data	!215371
Hide user data when display_gitlab_credits_user_data is false	👈 you're here

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