Resolve "Issue weight empty state in sidebar doesn't match other blocks"

Changes issue weight section in the issuable sidebar to match the other sections when there is an empty state.

Before:

After:

Does this MR meet the acceptance criteria?

• [ ] Changelog entry added, if necessary
• [ ] Documentation created/updated
• [ ] API support added
• Tests
  • [ ] Added for this feature/bug
  • All builds are passing
• Conform by the merge request performance guides
• Conform by the style guides
• Branch has no merge conflicts with master (if it does - rebase it please)
• Squashed related commits together

What are the relevant issue numbers?

Closes #2010 (closed)