[E2E] PROMOTE TO BLOCKING: merge_merge_request_from_fork_spec.rb

What does this MR do?

Promotes the following e2e tests to the blocking bucket:

1. Create Merge request creation from fork can merge source branch from fork into upstream repository | Testcase | Spec metrics

This MR was created based on data from reliable e2e test report: #458802 (closed)

(This MR was automatically generated by gitlab_quality-test_tooling at 2024-04-29 18:37:24 UTC)