[QUARANTINE] [nightly] Create with merge request suggestions applies a single suggestion with a custom message

What does this MR do?

Quarantines the test Create with merge request suggestions applies a single suggestion with a custom message (https://gitlab.com/gitlab-org/gitlab/-/blob/master/qa/qa/specs/features/browser_ui/3_create/merge_request/suggestions/custom_commit_suggestion_spec.rb#L44)

This test has been found by Confiner to have failed 6 times, which exceeds the threshold of 3 times.

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

#396620 (closed)

(This MR was automatically generated by Confiner at 2023-03-17 01:17:52 UTC)