Merge Request V2 Widget collapse button is slightly misaligned

Summary

The Merge Request V2 Widget is slightly misaligned compared to the V1.

Implementation plan

• Adjust margin/padding here: https://gitlab.com/gitlab-org/gitlab/-/blob/master/app/assets/javascripts/vue_merge_request_widget/components/widget/widget.vue#L338

Verification steps

• Go to gitlab-examples/security/security-reports!52 (closed)
• Check that the collapse icons are aligned