Hide mirror admin actions from developers

What does this MR do?

To trigger a pull or push mirror update, you need to be a project admin. However, we show the link to developers at the moment.

This is an issue for both pull and push mirrors.

Fix it by hiding the link if it's going to 404.

Screenshots

Developer or administrator before:

Does this MR meet the acceptance criteria?

Anonymous:

Developer after:

Conformity

• Changelog entry
• [-] Documentation (if required)
• Code review guidelines
• Merge request performance guidelines
• Style guides
• [-] Database guides
• Separation of EE specific content

Availability and Testing

• Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.
• [-] Tested in all supported browsers

Security

If this MR contains changes to processing or storing of credentials or tokens, authorization and authentication methods and other items described in the security review guidelines:

• [-] Label as security and @ mention @gitlab-com/gl-security/appsec
• [-] The MR includes necessary changes to maintain consistency between UI, API, email, or other methods
• [-] Security reports checked/validated by a reviewer from the AppSec team

Related to #35305 (closed)