Rename ci minute usage to admin minute usage quota

What does this MR do and why?

Pre-work for #346935 (closed)

Currently we have a read_ci_minutes_usage ability which is checked before rendering a notification to namespace owners when namespace owners are approaching or over the limit on minutes.

Here we make 2 changes to the read_ci_minutes_usage ability.

• Here we rename the :read_ci_minutes ability to :admin_ci_minutes since it should represent the ability to purchase minutes or view the usage quota page with a breakdown of how ci minutes are being used.
  • Customers who can read builds are be allowed to see the total usage and quota summary but not the full breakdown of the usage quota.
• Remove the admin_ci_minutes ability from project policy since only group owners can see the usage quota breakdown page and purchase minutes as documented. The notifications where this ability is currently used are only check the namespace anyways so we never actually check if this ability is allowed on a project.

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