Group Roadmap enhancements

What does this MR do?

Fixes following issues from Group-level Roadmap;

• Add shadow at bottom of the list when list is scrollable
• Fixes unnecessary spacing in blank list header
• Fixes Karma failure which started happening due to date change post Feb 28. See https://gitlab.com/gitlab-org/gitlab-ee/issues/5088.

Screenshots

TBA

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• [ ] Documentation created/updated
• [ ] API support added
• Tests added for this feature/bug
• Review
  • Has been reviewed by UX
  • Has been reviewed by Frontend
  • [ ] Has been reviewed by Backend
  • [ ] Has been reviewed by Database
• Conform by the merge request performance guides
• Conform by the style guides
• Squashed related commits together
• [ ] Internationalization required/considered
• [ ] If paid feature, have we considered GitLab.com plan and how it works for groups and is there a design for promoting it to users who aren't on the correct plan
• End-to-end tests pass (package-qa manual pipeline job)

What are the relevant issue numbers?

#4848 (closed)

Closes #5088 (closed).