[E2E] PROMOTE TO BLOCKING: add_file_template_spec.rb

What does this MR do?

Promotes the following e2e tests to the blocking bucket:

1. Create File templates user adds .gitlab-ci.yml via file template Julia | 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 02:05:11 UTC)