[E2E] PROMOTE TO BLOCKING: create_merge_request_spec.rb

What does this MR do?

Promotes the following e2e tests to the blocking bucket:

1. Create Create a new merge request creates a merge request with a milestone and label | Testcase | Spec metrics

This MR was created based on data from reliable e2e test report: #451727 (closed)

(This MR was automatically generated by gitlab_quality-test_tooling at 2024-03-25 02:04:38 UTC)