Update permission check for external status

What does this MR do and why?

Update permission check for external status to allow non-member admins to visualize the external status check.

Related to: #478783 (closed)

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

How to set up and validate locally

1. Create a project with a non-admin user
2. Configure an MR status check
3. Create an MR
4. Visit the MR page using an admin user
5. Check if the status check is visible