[QUARANTINE] [nightly] Verify when pipeline is blocked can still merge MR successfully

What does this MR do?

Quarantines the test Verify when pipeline is blocked can still merge MR successfully (https://gitlab.com/gitlab-org/gitlab/-/blob/master/qa/qa/specs/features/browser_ui/4_verify/pipeline/merge_mr_when_pipline_is_blocked_spec.rb#L71)

This test has been found by Confiner to have failed 5 times, which exceeds the threshold of 3 times.

1. ee:instance-image-slow-network
2. ce:upgrade
3. ee:nplus1-instance-image
4. ce:airgapped
5. ee:airgapped

#411510 (closed)

(This MR was automatically generated by Confiner at 2023-05-17 13:35:22 UTC)