Background Migrations - Header Margin Followup

What/Why

Based on @nickbrandt suggestion here: !85639 (comment 935566166)

We have some rogue margin hanging on the mobile view of admin/background_migrations😞

Screen_Shot_2022-05-05_at_11.04.09_AM

Thoughts

We should actually move the margin right on the title element over to margin-left on the Listbox element since it is conditionally there. This way we never have rogue margin.

However we only want the margin on > sm screens. So we first need to add the class to GitLab UI

Proposal

  1. Add .gl-sm-ml-7 to https://gitlab.com/gitlab-org/gitlab-ui
  2. Remove the .gl-mr-7 introduced in !85639 (merged)
  3. Add .gl-sm-ml-7 and .gl-ml-0 to the conditional listbox element js-database-listbox introduced in !85639 (merged)

note: All class changes are to be done in this file: https://gitlab.com/gitlab-org/gitlab/-/blob/master/app/views/admin/background_migrations/index.html.haml