Migrate spec/javascripts/related_merge_requests/ to Jest

Description

Let's migrate the specs in spec/javascripts/related_merge_requests/ from Karma to Jest.

See the related epic for how to do this.

• spec/javascripts/related_merge_requests/components/related_merge_requests_spec.js !32510 (merged)
• spec/javascripts/related_merge_requests/store/mutations_spec.js !32510 (merged)
• spec/javascripts/related_merge_requests/store/actions_spec.js !32510 (merged)