Relax force pull mirror update restriction

What does this MR do?

We currently allow force pull mirror update via API and web UI if the mirror wasn't updated within the last 5 minutes.

This affects pull mirrors that use SSH key authentication as they will fail initially because the public key has to be added to the source server. As a result, user have to wait 5 minutes before they can retry. This also resulted to a QA spec to fail.

This change will fix it by not restricting force mirror updates on mirrors that were never successfully updated.

Does this MR meet the acceptance criteria?

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
• [-] Informed Infrastructure department of a default or new setting change, if applicable per definition of done

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

Closes #216534 (closed)