Resolve "User profile page: Horizonal whitespace between Overview columns breaks two column layout"

What does this MR do?

The change introduced in https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/23803 creates a visual glitch for the single-column layout on smaller devices.

This MR makes sure that the additional horizontal 5px margin is only added on large breakpoints as long as there's a two-column layout.

Screenshots:

before	after

What are the relevant issue numbers?

https://gitlab.com/gitlab-org/gitlab-ce/issues/56010

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• Documentation created/updated
• Tests added for this feature/bug
• Tested in all supported browsers
• Conforms to the code review guidelines
• Conforms to the merge request performance guidelines
• Conforms to the style guides
• Conforms to the database guides
• Link to e2e tests MR added if this MR has Requires e2e tests label. See the Test Planning Process.
• Security reports checked/validated by reviewer

Closes #56010 (closed)