Fix Direct Transfer scopes copy to be precise

What does this MR do and why?

Our docs mention:

https://gitlab.com/gitlab-org/gitlab/-/blob/aa8c8c8a69cf67144e6ec129e10990b4cebda7d0/doc/user/group/import/direct_transfer_migrations.md#configuration

For GitLab 15.1 and later source instances, the personal access token must have the api scope. For GitLab 15.0 and earlier source instances, the personal access token must have both the api and read_repository scopes.

This change updates the copy in our UI to accurately reflect this.

https://gitlab.com/gitlab-org/gitlab/-/issues/509709#note_2261447783

MR acceptance checklist

Please evaluate this MR against the MR acceptance checklist. It helps you analyze changes to reduce risks in quality, performance, reliability, security, and maintainability.

Screenshots or screen recordings

Screenshots are required for UI changes, and strongly recommended for all other merge requests.

Before	After

How to set up and validate locally

Visit http://gdk.test:3000/groups/new#import-group-pane.

Related to #509709