[E2E] PROMOTE TO BLOCKING: pull_mirroring_over_ssh_with_key_spec.rb

What does this MR do?

Promotes the following e2e tests to the blocking bucket:

1. Create Pull mirror a repository over SSH with a private key configures and syncs a (pull) mirrored repository | Testcase | Spec metrics

This MR was created based on data from reliable e2e test report: #454762 (closed)

(This MR was automatically generated by gitlab_quality-test_tooling at 2024-04-08 02:05:31 UTC)